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L.  B.   Cat.   No.   II37 

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10018 


TEXT-BOOK  OF  POMOLOGY 


^\)c  Hural  tH^crt^llBoofe  Series; 

Edited  by  L.  H.  BAILEY 

Carleton:  The  Small  Grains. 

B.  M.  Duggar:  The  Physiology  of  Plant 
Production. 

J.  F.  Duggar:  Southern  Field  Crops. 

Fisk:  The  Book  of  Ice-Cream. 

Gay:  Breeds  of  Live-Stock. 

Gay:  Principles  and  Practice  of  Judging 
Live-Stock. 

Goff:  Principles  of  Plant  Culture. 

Gourley:  Text-Book  of  Pomology. 

Guthrie:  The  Book  of  Butter. 

Harper:  Animal  Husbandry  for  Schools. 

Harris  and  Stewart:  The  Principles  of 
Agronomy. 

Hitchcock:  Text-Book  of  Grasses. 

Jeffery:  Text-Book  of  Land  Drainage. 

Jordan.:  Feeding  of  Animals,  Revised. 

Livingston:  Field  Crop  Production. 

Lyon:  Soils  and  Fertilizers. 

Lyon,  Fippin  and  Buckman:  Soils;  Their 
Properties  and  Management. 

Mann:  Beginnings  in  Agriculture. 

Montgomery:  The  Corn  Crops. 

Morgan:  Field  Crops  for  the  Cotton- 
Belt. 

Mumford:  The  Breeding  of  Animals. 

Piper:  Forage  Plants  and  their  Culture. 

Sampson:  Effective  Farming. 

Smith:  Agricultural  Meteorology. 

Thorn  and  Fisk:  The  Book  of  Cheese. 

Warren:  Elements  of  Agriculture. 

Warren:  Farm  Management. 

Wheeler:  Manure  and  Fertilizers. 

White:  Principles  of  Floriculture. 

Widtsoe:  Principles  of  Irrigation  Prac- 
tice. 


TEXT-BOOK  OF 
POMOLOGY 


BY 
J.  H.  GOURLEY,  M.  S. 

HORTICULTURIST,   OHIO  AGRICULTURAL  EXPERIMENT  STATION 

FORMERLY     PROFESSOR    OF    HORTICULTURE 

NEW    HAMPSHIRE    COLLEGE 


5^pm  fork 

THE  MACMILLAN  COMPANY 

1923 


All  rights  reserved 


\S\(^ 


Copyright,  1922 
By  the  MACMILLAN  COMPANY 


Set  up  and  electrotyped.     Published  August,  1922. 


Printed  in  the  United  States  of  America 


LIBRARY 

M  C.  state  College 


PREFACE 

The  purpose  of  this  book  is  to  present  the  experimental 
and  investigational  bases  of  fruit-growing  on  the  physiological 
side,  omitting  consideration  of  the  systematic  botany  and 
taxonomy  as  well  as  of  pathology.  Pomology  has  here- 
tofore been  approached  mostly  from  the  orchard-practice 
side,  born  of  the  experience  of  cultivators.  Gradually  the 
underlying  physiological  and  chemical  reasons  for  the  suc- 
cess of  these  practices  are  being  uncovered.  It  is  on  these 
rational  bases  that  college  teaching  must  henceforth  largely 
rest. 

In  the  preparation  of  the  present  volume,  it  is  assumed  that 
the  student  is  familiar  with  the  more  common  orchard  prac- 
tices, which  statement  will  explain  the  omission  of  much  in- 
formational material.  It  has  been  apparent  for  some  time 
that  much  of  the  experimental  results  which  have  been  ac- 
cumulating from  year  to  year  should  be  collected  into  con- 
venient form  for  students,  for  it  should  be  the  purpose  of 
the  student  to  study  (not  merely  read)  the  science  on  which 
present-day  practices  in  fruit-production  are  based.  It  may 
seem  to  some  persons  that  we  have  here  gone  far  afield  for 
much  of  the  material,  but  the  more  careful  work  of  recent 
years  has  made  use  of  nearly  all  the  sciences  in  attempting 
to  solve  the  problems. 

It  is  doubtless  true  that  the  advance  which  agricultural 
education  is  making  in  secondary  schools  will  force  the  col- 
legiate work  into  a  still  more  advanced  position  and  much  of 
the  material  formerly  used  with  satisfaction  will  give  place 
to  more  technical  and  scientific  matter.  This  means,  on 
the  one  hand,  that  the  college  class-room  work  will  lie  more 

10018 


VI  PREFACE 

in  underlying  principles  than  in  practices,  and  on  the  other, 
that  the  laboratory  and  the  supervised  summer  instruction 
will  become  still  more  practical;  and  this  we  believe  will 
meet  with  the  approval  of  the  best  informed  fruit-growers 
as  well  as  educators. 

In  the  preparation  of  this  book,  the  author  has  drawn 
freely  from  the  work  of  others.  He  has  also  invited  several 
of  his  colleagues  to  make  suggestion  and  criticism  of  parts 
of  the  manuscript.  However,  in  no  case  was  the  final  copy 
submitted  and,  therefore,  any  errors  that  may  occur  devolve 
entirely  on  the  author.  He  is  particularly  indebted  to  Dr. 
E.  J.  Kraus  who  offered  many  helpful  suggestions  and  as- 
sisted in  the  interpretation  of  some  of  the  experimental  work. 
Similarly,  Dr.  F.  E.  Bear  assisted  with  Chapters  VIII  and 
IX,  and  Dr.  M.  J.  Dorsey  with  Chapter  XIII.  Others  who 
read  portions  of  the  manuscript  were  Drs.  W.  H.  Chandler, 
J.  K.  Shaw,  H.  R.  KraybiU  and  Prof.  W.  Paddock.  To 
James  Macfarlane  and  J.  L.  Hayman  thanks  are  due  for 
their  kindness  in  preparing  several  of  the  drawings. 

Wooster,  Ohio,  J.  H.  GoURLEY. 

April  1,  1922. 


TABLE   OF   CONTENTS 

(Numbers  in  the  text  refer  to  paragraphs) 
CHAPTER  I 

PAGES 

The  Composition  of  Fruits 1-18 

Composition  of  apple  leaves,  1;  Composition  of  apple 
fruit,  2;  Ash  of  fruits,  3;  Forms  of  sugar  in  fruits,  4;  Sugar- 
content  of  ripe  fruit  juices,  5;  The  essential  oils,  6;  Quality 
in  apples,  7;  The  effect  of  location  on  quality,  8;  Composi- 
tion of  fruits  grown  on  irrigated  and  non-irrigated  land,  9; 
Chemical  changes  in  the  growing  apple,  10;  Composition 
of  apples  in  common  storage,  11;  Changes  in  composition 
of  the  peach  during  growth  and  ripening,  12;  Ripening 
process  in  pears,  13. 

CHAPTER  II 

The  Buds  of  Fruit-Trees 19-33 

Buds  defined,  14;  Gross  structure,  15;  Classification  of 
buds,  16;  Leaf-buds,  17;  Fruit-buds,  18;  Flower-buds,  19; 
Simple  buds,  20;  Mixed  buds,  21;  Terminal  and  lateral 
buds,  22;  Latent  buds,  23;  Adventitious  buds,  24;  Col- 
lateral buds,  25;  Leaf-scars,  26;  Fruit-spurs,  27;  Fruiting 
of  the  apple,  28;  Fruiting  of  the  pear,  29;  Fruiting  of  the 
peach,  30;  Fruiting  of  the  cherry,  31 ;  Fruiting  of  the  plum, 
32;  Fruiting  of  the  apricot,  33;  Fruiting  of  the  quince,  34; 
Fruiting  of  the  grape,  35. 

CHAPTER  III 

The  Differentiation  of  Flower-Buds 34-49 

The  apple,  36;  Sepals,  37;  Petals,  38;  Stamens,  39;  Car- 
pels, 40;  The  peach,  plum  and  cherry,  41;  Inflorescence, 
42;  The  flowering  branch,  43;  Vascular  anatomy,  44; 
The  carpellary  system,  45;  Comparative  morphology  of 
fruits,  46. 

CHAPTER  IV 

Factors  which  Influence  Fruit-Bud  Formation 50-73 

Vegetative  and  reproductive  processes,  47;  The  periodic 


TABLE  OF  CONTENTS 


PAGES 

idea,  48;  Theory  of  specific  constructive  materials,  49; 
Reserve  food,  50;  Carbohydrates,  nitrogen-complexes  and 
moisture,  51;  Relation  of  these  materials  to  flowering  of 
plants,  52;  Relation  of  leaf  area  to  flowering,  53;  Effect  of 
leaves  on  parts  immediately  surrounding  them,  54;  Horti- 
cultural practices  that  influence  fruit-bud  formation,  55; 
Cultural  practices,  56;  Pruning,  57;  Ringing,  58;  Stripping, 
59;  Bending,  60;  Dwarfing,  61;  Thinning,  62;  Individual- 
ity, 63;  Climate,  64;  Plants  threatened  by  death,  65;  Light, 
66;  Biennial  bearing,  67. 


CHAPTER  V 

Pruning 74-101 

Definition,  68;  Objects  of  pruning,  69;  Shape  or  form  of 
the  tree,  70;  The  type  of  tree  to  be  developed,  71;  Obtain- 
ing the  ideal,  72;  Fruiting  system  of  the  tree,  73;  Effect  of 
pruning  on  size  and  development  of  trees,  74;  Effect  of 
pruning  on  early  bearing,  75;  Effect  of  the  unequal  cut,  76; 
Heading-back  versus  thinning-out,  77;  Detailed  response 
of  young  trees,  78;  Relation  of  pruning  to  nutrition,  79; 
Theoretical  considerations,  80;  When  to  prune,  81;  Prun- 
ing at  planting  time,  82;  Pruning  young  versus  mature 
trees,  83;  Salient  features  in  pruning  mature  trees,  84; 
Renovation  pruning,  85;  Summer  pruning,  86. 


CHAPTER  VI 

'he  Thinning  of  Fruit 102-123 

Definition,  87;  History  of  thinning,  88;  Philosophy  of 
thinning,  89;  Fruit  production  exhaustive,  90;  Dependence 
of  fruits  on  foliage  immediately  surrounding  it,  91;  Ob- 
jects of  thinning,  92;  To  increase  the  size  of  the  fruit,  93; 
Thinning  to  improve  color,  94;  Quality  improved  by 
thinning,  95;  Thinning  to  prevent  breaking  of  limbs,  96; 
Thinning  to  reduce  disease  and  insect  injury,  97;  Thinning 
to  maintain  the  vigor  of  the  trees,  98;  Thinning  to  secure 
more  regular  bearing,  99;  Thinning  to  decrease  the  labor 
of  handling  excessive  crops  of  small  fruit,  100;  The  effect 
of  thinning  on  the  total  crop,  101 ;  When  to  thin,  102;  The 
June  drop,  103;  How  to  thin,  104;  Distance  to  thin,  105; 
Cost  of  thinning  versus  returns,  106;  Thinning  the  peach, 
107;  Thinning  the  plum,  108;  Thinning  the  pear,  109; 
Thinning  the  grape,  110. 


TABLE  OF  COX  TENTS  ix 

CHAPTER  VII 

PAGES 

Orchard  Soils 124-141 

Factors  involved,  111;  Soils  defined,  112;  Soil  classifica- 
tion, 113;  Soils  and  subsoils,  114;  Mechanical  analysis  of 
fruit  soils,  115;  Orchard  soils,  116;  Chemical  nature  of 
fruit  soils,  117;  Soil  color,  118;  Limestone  soils,  119;  Alka- 
line soils  ,120;  Drainage,  121;  Organic  matter,  122;  Adap- 
tation of  fruit  to  soil  types,  123. 

CHAPTER  VIII 

Cultural  Methods  in  Orchards 142-178 

Systems  of  cultivation,  124;  Terms  defined,  125;  Sod 
culture,  126;  Grass  mulch,  127;  Production  of  mulch  ma- 
terial, 128;  Clean  cultivation,  129;  Tillage  and  cover-crop 
system,  130;  Cover-crops,  131;  Nitrification,  132;  Value  of 
cover-crops  in  California,  133;  Effects  of  cultural  methods 
on  the  soil,  134;  Effect  of  moisture,  135;  Effect  of  tempera- 
ture, 136;  Nitrates,  137;  Is  nitrification  retarded  under 
sod?  138;  The  toxic  theory,  139;  Effect  of  cultural  systems 
on  the  growth  of  the  trees,  140;  Leaf  area,  141;  The  Wo- 
burn  experiments,  142;  Yield  of  fruit,  143;  Sod,  tillage  and 
mulch  for  the  apple,  144;  Cultivation  for  the  peach,  145; 
Fall  plowing  the  orchard,  146;  Use  of  explosives  for  tillage 
purposes,  147. 

CHAPTER  IX 

Fertilizers  and  Manures  pqR  the  Orchard 179-217 

Criticisms  of  orchard  experiments,  148;  Fertility  re- 
moved by  fruit-trees,  149;  Fruit-trees  essentially  different 
from  other  crops,  150;  Amount  of  food  materials  found  in 
plants  not  a  guide,  151;  Analysis  of  the  soil  as  a  guide  to 
fertilizing,  152;  Necessity  of  fertilizing  orchards,  153;  Fer- 
tilizing tilled  and  non-tilled  apple  orchards,  154;  Moisture 
and  fertility  intimately  related,  155;  Relative  importance 
of  the  different  essential  elements,  156;  Organic  versus  in- 
organic fertilizers,  157;  Value  of  nitrogen,  158;  Nitrate  of 
soda,  159;  Sulfate  of  ammonia,  160;  Time  of  application, 
161;  Phosphorus,  162;  Acid  phosphate,  163;  Potash,  164; 
Muriate  versus  sulfate  of  potash,  165;  Hardwood-ashes, 
166;  Common  salt,  167;  Animal  manures  in  the  orchard, 
168.  Experiments  in  Uyililled  Orchards:  The  Massachusetts 
experiment,  169;  The  Ohio  experiments,  170;  The  Penn- 
sylvania experiments,  171;  New  Hampshire  experiments, 


X  TABLE  OF  CONTENTS 

PAGES 

172.  Experiments  in  Tilled  Orchards:  The  Woburn  experi- 
ment, 173;  The  New  York  experiments,  174;  The  New 
Hampshire  experiments,  175;  The  Maine  experiment,  176; 
The  Oregon  experiments,  177;  West  Virgmia  experiment, 
178;  The  Pennsylvania  experiments,  179;  The  Ohio  ex- 
periments, ISO;  Results  compared,  181.  Other  Results  of 
Fertilizing:  Color  of  fruit,  182;  FertiHzing  the  peach,  183; 
Effect  of  fertihzing  on  regular  bearing,  184;  AppHcation  of 
fertihzers,  185;  Size  of  fruit,  186;  Summary,  187. 

CHAPTER  X 

The  Relation  of  Climate  to  Pomology 218-253 

Terms  defined,  188;  Rekition  of  weather  to  the  fruit 
crops,  189;  Temperature,  190;  Rainfall,  191;  Spring  frosts, 
192;  Winds,  193;  Sunshine,  194;  Hail,  195;  Continental 
versus  marine  climates,  196;  Mountain  versus  valley  cli- 
mates, 197;  Climate  of  United  States,  198;  Climatic  prov- 
inces of  the  United  States,  199;  The  Eastern  province, 
200;  The  Gulf  province,  201;  The  Plains  province,  202; 
The  Plateau  province,  203;  The  Pacific  province,  204; 
Natural  guides  to  horticultural  practices,  205;  Bioclimatic 
law  of  latitude,  longitude,  and  altitude,  206;  Species 
adaptation,  207;  Temperatures  which  injure  setting  of 
fruits,  208;  Averting  injury  from  frosts  and  freezes,  209; 
Effect  of  climate  on  the  floral  structure,  210;  The  effect  of 
climate  on  development  of  fruit,  211;  Climatic  factors 
which  delimit  the  geographical  distribution  of  fruits,  212; 
Specific  requirements  for  certain  varieties,  213.  Pheno- 
logical  Studies:  The  physiological  constant,  214;  The 
blooming  season,  215;  Comparative  blooming  dates,  216; 
Duration  of  blooming  period,  217;  Period  of  ripening  of 
hardy  fruits,  218;  Relation  between  blooming  and  ripen- 
ing, 219;  Form  for  recording  phenological  data,  220. 

CHAPTER  XI 

Winter  Injury 254-281 

Bud  injury,  221;  Injury  to  the  woody  parts  above 
ground,  222;  The  killing  of  the  terminals,  223;  Killing  of 
patches,  224;  Crotch  injury,  225;  Collar-rot,  226;  Frost- 
cracks,  227;  "Black  heart,"  228;  Sun-scald,  229;  Root- 
kiUing,  230;  How  freezing  kills,  231;  Hardiness  of  different 
tissues,  232;  Rest-period,  233.    Factors  Involved  in  Freezing: 


TABLE  OF  CONTENTS  xL 

PAGES 

Maturity,  234;  Sap  concentration,  235;  Rate  of  freezing  a 
factor,  236;  Protection  of  bud-scales,  237;  Relation  of  crop 
the  preceding  season,  238;  Correlation  of  wood  structure 
and  hardiness,  239;  Influence  of  type  of  soil,  240;  Proxim- 
ity to  bodies  of  water,  241;  Topography  of  land,  242; 
Winds,  243.  Orchard  Practices:  Cultivation,  244;  Pruning, 
245;  Protecting  trees  and  buds,  246;  Securing  hardier 
fruits,  247;  Treatment  of  frozen  trees,  248;  Variation  in 
hardiness  of  fruits,  249;  Hardy  and  tender  varieties,  250; 
The  grape,  251. 

CHAPTER  XII 

Pollination  and  the  Sterility  Problem 282-310 

Investigations  in  pollination,  252;  Causes  of  unfruitful- 
ness,  253;  Development  of  pollen,  254;  Germination  of  the 
pollen,  255;  Longevity  and  viability  of  pollen,  256;  Length 
of  receptive  condition  of  the  stigma,  257;  Fertilization, 
258;  Cross-pollination,  259;  Means  of  effecting  cross- 
pollination,  260;  Nature's  methods  of  avoiding  self- 
pollination,  261;  Effect  of  cross-pollination  on  the  fruit, 
262;  Effect  of  seed-bearing  on  the  fruit,  263;  Artificial 
pollination,  264.  The  Sterility  Problem:  Definition  of 
terms,  265;  Sterility  not  a  constant  factor,  266;  Causes  of 
sterility,  267;  The  cherry,  268;  The  almond,  269;  The 
grape,  270;  The  plum,  271;  The  peach,  272;  The  quince, 
273;  The  apple,  274;  The  pear,  275. 

CHAPTER  XIII 

The  Origin  and  Improvement  of  Fruit 311-338 

Theory  of  Van  Mons,  276;  Work  of  Knight,  277;  Selec- 
tion as  a  means  of  securing  new  fruits,  278;  Mass-selec- 
tion, 279;  Line-selection,  280;  Clonal-selection,  281;  Bud- 
selection,  282;  Individuality  of  fruit-trees,  283;  Results  of 
selecting  bud  variations,  284;  Plant  introduction,  285; 
Chance  seedlings,  286;  Work  in  Canada,  287;  Work  of 
Peter  Gideon  and  other  pioneers  in  the  United  States, 
288;  Hansen  hybrids,  289;  Burbank's  work,  290;  Inheri- 
tance of  characters  in  the  apple,  291;  The  heterozygous 
nature  of  fruits,  292;  Pedigreed  nursery  stock,  293;  Graft- 
hybrids,  294;  Breeding  the  grape,  295;  Inheritance  of  self- 
sterility  in  grapes,  296;  The  inheritance  of  sex  in  the  grape, 
297;  Rogers'  hybrids,  298;  Breeding  disease-resistant 
fruits,  299;  Stocks  for  pears,  300;  Stock  for  grapes,  301. 


xii  TABLE  OF  CONTENTS 


CHAPTER  XIV 

Propagation  and  Fruit-Stocks 339-355 

Handling  the  seed  and  stock,  302;  The  more  common 
fruit-stocks,  303;  Apple  stocks,  304;  Pear  stocks,  305; 
Quince  stocks,  306;  Peach  stocks,  307;  Plum  stocks,  308; 
Cherry  stocks,  309;  Quarantine  measures,  310;  Importa- 
tions of  stock,  311;  Fruit-trees  on  their  own  roots,  312;  Re- 
lation of  cion  and  stock,  313.  Propagation  of  Fruit-Trees: 
Mound-layerage,  314;  cuttings,  315;  Grafting  and  budding, 
316;  Tongue-graft  or  whip-graft,  317;  Budding,  318;  June- 
budding,  319;  Double-working  of  apple  trees,  320. 

CHAPTER  XV 

Storage  of  Fruit 356-369 

Definition,  321;  History  of  storage,  322;  Types  of  stor- 
age, 323 ;  The  function  of  storage,  324 ;  Factors  influencing 
the  keeping  quality  of  fruit,  325;  Maturity  of  fruit,  326; 
Effect  of  over-maturity,  327;  Effect  of  delayed  storage, 
328;  The  storage  temi)erature,  329;  Influence  of  a  fruit 
wrapper,  330;  Influence  of  cultural  conditions,  331;  Type 
of  package  for  storage,  332;  The  shrinkage  of  fruit  in  stor- 
age, 333;  Apple-scald,  334;  Pre-cooling,  335;  Methods  of 
pre-cooling,  336. 


LIST   OF   ILLUSTRATIONS 

PLATES  FACING  PAGE 

I.  a,  Showing  reduction  in  flowering,  elongation  of  internodes, 
and  increased  area  to  a  leaf  due  to  shading,    b,  Showing 

effect  of  shading  a  peach  tree 38 

II.  a,  An  open-headed  apple  tree,     b,  A  two-story  apple  tree 

with  sets  of  scaffolds  too  close  together 78 

III.  a,  Dwarf  apple  trees  trained  in  a  horizontal  cordon,  espalier 

pear  trees  on  wall  to  rear,  b,  A  type  of  central  leader 
that  could  now  be  developed  either  into  a  two  or  a  three- 
story  tree,  c,  An  unpruned  apple  tree  that  has  developed 
as  a  central  leader,  d,  A  two-story  tree  with  four 
branches  at  each  scaffold 116 

IV.  Six-year-old  sour  cherry  trees,    a,  Unpruned;  6,  moderately 

pruned;  c,  heavily  pruned;  d,  summer  pruned 154 

V.  a,  Fruit  from  an  unthinned  Baldwin  apple  tree,     b,  Fruit 

from  a  thinned  Baldwin  tree.    (Courtesy  Ohio  Exp.  Sta.)   198 
\l.  In  the  background  is  shown  the  effect  of  acid  phosphate  on 
the  natural  growth  of  clover  in  the  Ohio  experiments. 

(After  F.  H.  Ballon,  Ohio  Agr.  Exp.  Sta.  Bull.  301) 246 

VII.  a,  Trees  grown  permanently  in  sod.  b,  Trees  grown  under 
the  gra.ss-mulch  system,  c,  The  tillage-cover-crop  sys- 
tem used  in  this  orchard.     (Ind.  Agr.  Exp.  Sta.) 298 

VIII.  o,  The  twig  terminals  of  these  Baldwin  apple  trees  were  killed 
in  winter  of  1917-18.  b,  A  winter-injured  peach  tree 
that  was  not  cut  back 348 

FIGURES  PAGB 

1.  Curves  showing  the  average  chemical  changes  in  the  growing 

apple  (Bigelow,  W.  D.,  H.  C.  Gore  and  B.  J.  Howard,  U.  S. 
Dept.  Agr.  Bur.  Chem.  Bull.  94) 11 

2.  Curves  showing  chemical  changes  in  Rhode  Island  Greening 

apple  in  common  storage.    (Bigelow,  W.  D.,  H.  C.  Gore,  and 

B.  J.  Howard,  U.  S.  Dept.  Agr.  Bur.  Chem.  Bull.  94) 13 

3.  Fruit  production  and  two  axillary  shoots,  all  arising  from  a 

single  fruit-bud.     (Rome) 22 

4.  Short  spurs  of  apple  bearing  tenninal  fruit-buds 25 

5.  Axillary  and  terminal  fruit-bud  formation  in  the  apple 27 

xiii 


xiv  LIST  OF  ILLUSTRATIONS 

FIGURES  PAGE 

6.  The  beginning  of  a  fruit-spur  system  in  the  apple 27 

7.  A  flower-cluster  base  that  has  produced  a  fruit-bud  and  a  long 

shoot.    (Rome  apple) 28 

8.  Branched  fruit-spur  system  of  the  apple 28 

9.  Axillary  fruit-bud  formation  in  the  pear 29 

10.  A  vigorous  fruit-spur  of  the  pear 30 

1 1 .  Fruiting  habit  of  the  peach 30 

12.  Fruiting  habit  of  the  sour  cherry.    A  strongly  vegetative  type  32 

13.  Floral  diagram  of  the  apple.     (After  E.  J.  Kraus,  Ore.  Agr. 

Exp.  Sta.  Research  Bull.  1,  part  1) 35 

14.  Early  stages  of  fruit-bud  differentiation  in  the  apple.     (After 

E.  J.  Kraus,  Ore.  Agr.  Exp.  Sta.  Research  Bull.  1,  part  1).  .     36 

15.  Diagram  indicating  positions  of  four  flower  primordia 37 

16.  Diagrammatic  representation  of  origin  of  calyx  primordia  on 

edge  of  torus 37 

17.  Diagram  showing  development  of  the  apple.     (After  E.  J. 

Kraus,  Ore.  Agr.  Exp.  Sta.  Bull.  1,  part  1) 42 

18.  Diagrammatic  drawing  of  an  apple  inflorescence  or  peduncle 

from  which  arise  the  pedicelled  flowers.    (After  C.  A.  Black, 

N.  H.  Agr.  Exp.  Sta.  Tech.  Bull.  10) 43 

19.  Showing  parts  of  a  flowering  branch 43 

20.  A,  medium  lengthwise  section  of  a  mature  apple;  B,  cross-sec- 

tion of  same.     (From  Robbins,  Botany  of  Crop  Plants,  by 
permission  of  P.  Blakiston's  Sons  Co.) 46 

21.  Diagram  illustrating  distribution  of  bundles  in  the  torus  and 

pedicel  apex.     (After  E.  J.  Kraus  and  G.  S.  Ralston.    Ore. 
Agr.  Exp.  Sta.  Bull.  138) 47 

22.  Diagram  to  illustrate  the  hypotheses  involved  in  Classes  I,  II, 

III,  and  IV 56 

23.  Diagrammatic  representation  of  arrangement  of  scaffold  limbs 

in  pruning 76 

24.  Showing  the  type  of  growth  that  commonly  follows  the  cutting 

of  the  terminal : 89 

25.  Showing  a  type  of  growth  that  follows  when  the  terminal  is  not 

removed.    The  buds  which  give  rise  to  shoots  are  usually  not 
confined  to  the  terminal  ones 90 

26.  A  graphic  representation  of  the  cycle  of  nitrogen  through  the 

plant  and  the  soil.     (After  M.  A.  Bachtel,  Ohio  Agr.  CgII. 
Ext.  Bull,  Vol.  8,  No.  1,  1912) 151 


LIST  OF  ILLUSTRATIONS  xv 

FIGURES  PAGE 

27.  Curves  showing  the  maximum  soil  temperatures  under  the  dif- 

ferent soil  treatments  in  an  orchard.  (After  Woodbury, 
Noyes  and  Oskamp,  Ind.  Agr.  Exp.  Sta.  Bull.  205) 158 

28.  Curves  showing  the  relative  formation  of  nitrates  under  sod, 

tillage,  and  tillage  cover-crop  systems  of  orcharding.  Parts 
per  million  dry  soil 161 

29.  Row  of  trees  to  left  was  fertilized  with  5  pounds  nitrate  of  soda 

to  each  tree.    The  one  to  right  untreated 200 

30.  Apple  tree  injured  by  hail  storm.    Note  abrasions  of  bark  and 

partial  defoliation 225 

31.  Length  of  growing  season  in  different  parts  of  the  United  States. 

(After  Henry) 229 

32.  Isophanal  map  of  North  America.    (After  Hopkins) 236 

33.  Map    showing   the   boundaries  of   the   Michigan   fruit-belt. 

(After  Seeley) 241 

34.  Fruit-bud  of  sour  cherry.    Left,  flower  bud  alive;  right,  flower- 

bud  killed 255 

35.  Winter  injury  on  trunk  of  a  Baldwin  apple  tree 256 

36.  Diagram  of  a  simple  pistil  as  seen  in  lengthwise  section,  show- 

ing a  single  ovule  just  prior  to  fertilization.  (From  Robbins' 
Botany  of  Crop  Plants,  by  permission  of  P.  Blakiston's  Sons 
Co.) 290 

37.  French  crab,  imported  apple  seedling.    (From  Bailey,  The  Nur- 

sery Manual,  by  permission  Macmillan  Co.) 341 

38.  The  tongue  or  whip-graft  of  apple 352 

39.  Shield-budding.     (From  Bailey,  The  Nursery  Manual,  by  per- 

mission Macmillan  Co.) 353 

40.  Method  of  double-working  the  apple 354 


TEXT-BOOK  OF  POMOLOGY 

CHAPTER  I 

THE  COMPOSITION  OF  FRUITS 

For  convenience,  the  composition  of  the  common  fruits 
may  be  divided  into  three  phases:  (1)  composition  of  the 
tree,  (2)  composition  of  the  fruits,  and  (3)  the  changes  in 
the  ripening  process  and  in  storage.  Unfortunately,  there 
is  not  as  great  uniformity  of  opinion  among  the  chemists 
in  regard  to  the  composition  of  fruits  as  might  be  wished 
for,  yet  many  experimental  data  are  available  and  are 
valua])le  for  the  present  purpose.  Different  chemical 
methods  in  analysis  and  widely  varjdng  material  account 
in  part  for  the  results  and  therefore  for  the  difference  of 
opinion.  While  it  is  not  possible  here  to  consider  the  analysis 
of  all  the  fruits,  some  of  the  more  important  ones  maj'-  be 
used  for  illustration. 

Table  I 


COMPOSITiON  OP  WOOD  AND  LEAVES  OF  TREES 

POUNDS  IN  100  (percentage)  ^ 

Wood 

Nitrogen 

Apple 
0.50 

Phosphoric  Acid 
P2O5 

0.15 

Potash 
K2O 

..0.25 

Leaves 

1.00 

Pear 

.0.15... 

..0.35 

Wood 

0.30 

.0.10... 

..0.25 

Leaves 

0.70 

Peach 

.0.12... 

..0.40 

Wood 

0.43 

.0.10... 

..0.22 

Leaves 

0.90 

.0.15... 

..0.60 

'iVan  Slyke, 
York,  1912. 

L. 

L. 

Fertilizers  and  Crops. 

1 

Orange 

Judd  Cc 

).,  New 

2  POMOLOGY 

1.  Composition  of  apple  leaves. — The  net  loss  in  fertility 
from  orchard  lands  is  somewhat  reduced  by  the  return  of 
the  leaves  to  the  soil.  True,  a  portion  of  them  is  blown 
from  the  orchard  and  hence  it  would  not  be  entirely  accurate 
to  assume  that  the  land  received  an  annual  fertilization  of 
the  full  amount  of  the  leaves  produced.  Thompson  ^  has 
shown  the  amount  of  fertility  represented  in  the  fall  of 
leaves  for  a  period  of  nine  years  as  follows: 

Table  II 


POUNDS  OF  PLANT-FOOD  TO  THE 
YEARS    OF    AGE 

ACRE  USED  IN  GROWING 
(after  THOMPSON) 

FREES  TO  NINE 

Peach  trees 

Apple  trees 

P2O5 

N 

K2O 

P2O5 

N 

K2O 

Total  plant-food  taken 
up  by  trees  in  9  years 

Total     plant-food     re- 
turned to  the  soil  by 
leaves,  etc 

Total     plant-food     re- 
tained in  trees  at  the 
9th  growing  season. .  . 

50.83 
23.16 

27.67 

215.90 
127.93 

87.97 

2.37.60 

177.42 
60.18 

9.26 
2.53 
6.73 

2S.10 
12.84 
15.26 

27.22 
12.97 
14.25 

"The  net  loss  in  soil  fertility  in  growing  an  orchard  to 
nine  years  of  age  is  represented  by  the  plant-food  retained 
in  the  trees  at  the  end  of  the  ninth  growing  season.  This 
table  [given  above]  is  based  on  the  assumption  that  the 
leaves  have  not  blown  away,  but  have  decayed  on  the  land. 
The  peach  trees  at  nine  years  of  age  had  reached  their 
maximum  size.  The  apple  trees  were  only  about  one-fifth 
to  one-eighth  their  maximum  size,  but  the  results  indicate 
that  an  acre  of  mature  apple  trees  would  take  from  the  soil 
about  the  same  amount  of  plant-food  as  an  acre  of  mature 
1  Thompson,  R.  C.    Ark.  Agr.  Exp.  Sta.  Tech.  BuU.  123. 


THE  COMPOSITION  OF  FRUITS 


peach  trees.  In  other  words,  the  approximate  total  loss  of 
plant-foods  in  growing  an  acre  of  apple  trees  to  their  maxi- 
mum size  would  be  five  to  eight  times  the  amount  shown 
in  the  table.  This  would  make  the  total  loss  of  fertility  in 
growing  an  acre  of  peach  or  apple  trees  to  maturity  approxi- 
mately equivalent  to  the  plant-food  contained  in  10  bushels 
of  corn.  This  is  surprisingly  small  and  shows  very  clearly 
that  soil  exhaustion  hi  orcharding  is  almost  entireh^  due 
to  the  removal  of  plant-food  in  the  fruit  crop." 

Shutt  ^  has  determined  the  analysis  of  the  leaves  of 
several  standard  varieties  of  apples  in  terms  of  composition 
of  the  ash,  as  follows: 

Table  III 

COMPOSITION  OF  APPLE  LEAVES  (AFTER  SHUTT) 


Composition  of 

Percentage  composition  of 
important  ash  constit^lents 

Nitrogen 

Average  of  five 
varieties 

3 
1 

P 

1 

1 

S 

ll 

Nitrogen 

in 
organic 
matter 

Taken  May  25 
Taken  Sept.  20 

72.36 
60.71 

2.5..31 
35.83 

2..33 
3.46 

10.47 

5.82 

10.82 
11.63 

17.40 
27.91 

9.77 
4.81 

1.07 
1.14 

1.49 
1.41 

2.94 

2.48 

From  these  data  it  will  ])e  seen  that  apple  leaves,  when 
practically  mature,  contain  35.83  per  cent  organic  matter 
which  may  be  returned  to  the  soil,  and  that  there  is  2.48 
per  cent  of  nitrogen  in  the  organic  matter.  Of  the  ash, 
5.82  per  cent  is  phosphoric  acid  and  11.63  per  cent  is  potash, 
or  the  relation  of  these  two  ingredients  in  the  mature  leaves 
is  2  to  1.  Thus  it  will  be  seen  that  there  is  twice  as  great  a 
demand  on  the  soil  for  potash  as  phosphoric  acid  so  far  as  the 
leaves  are  concerned.  As  will  be  seen  later,  the  ratio  is  still 
greater  in  the  ash  of  the  fruit  since  there  is  six  times  as 
much  potash  as  phosphoric  acid  present  there. 

1  Shutt,  F.  T.  The  chemistry  of  the  apple.  Ann.  Rept.  Can.  Dept. 
Agr.  Ottawa.     1894. 


4  POMOLOGY 

There  are  no  important  differences  between  the  ash  of  the 
separate  varieties  of  apples,  although  some  variations  occur. 

2.  Composition  of  apple  fruit. — The  degree  of  ripeness, 
the  variety,  and  the  place  where  grown  affect  the  chemical 
composition  of  apples.  In  general,  they  contain  from  75 
to  85  per  cent  of  water,  82  to  84  per  cent  being  rather  com- 
mon. The  total  solids  will  be  from  10  to  18  per  cent  of  the 
whole,  75  per  cent  of  which  is  sugar  or  aUied  carbohydrates, 
and  about  half  a  per  cent  each  is  fat  and  protein.^  These 
vary  markedly,  depending  on  the  variety.  Malic  acid  is 
the  predominating  organic  acid  in  apples  and  may  run  from 
.15  per  cent  to  more  than  1  per  cent.  Essential  oils  are 
also  present  and  are  responsible  in  no  small  degree  for  the 
flavor  of  the  fruit,  but  they  are  not  easily  handled  by  the 
chemist  and  only  recently  have  they  been  separated  and 
expressed  in  terms  of  percentage  of  the  fruit. 

Table  IV 

COMPOSITION    OF    NORMAL    MATURE     FRUIT    OF    RED    ASTRACHAN    APPLE 
(adopted  from  CULPEPPER,  FOSTER  AND  CALDWELL)  ^ 


Analyst 

Sources  of  fruit 

Total 

Ash 

Acidity 

Crude 

Reduc- 
ing 

Cane 

Pro- 

solids 

malic 

fiber 

sugar 

sugar 

tein 

Per 

Per 

Per 

Per 

Per 

Per 

Per 

cent 

cent 

cent 

cent 

cent 

cent 

cent 

Browne  .  . 

State  College,  Pa. 

15.30 

0.37 

1.038 

6.67 

3.53 

Jones  & 

Non-irrigated 

Colver 

orchard,  Idaho 

18.10 

.94.57 

6  98 

2.15 

0.288 

Jones  & 

Irrigated  orchard, 

Colver 

Idaho 

14.73 

.890 

6,08 

2.91 

.560 

Culpepper, 

Foster  & 

Auburn,  Ala. 

12.94 

.2548 

.9288 

2.10 

.574 

4.960 

.245 

Caldwell 

3.  Ash  of  fruits. — According  to  Colby,^  apples  and 
pears  withdraw  less  mineral  matter  from  the  soil  than  do 

^  Culpepper,  C.  W.,  A.  C.  Foster,  and  J.  S.  Caldwell,  Jour.  Agr.  Res. 
7:  17-40.     1916. 

2  Colby,  G.  E.  Ann.  Rept.  Calif.  Agr.  Exp.  Sta.  1897-98.  pp.  143- 
148. 


THE  COMPOSITION  OF  FRUITS  5 

many  other  orchard  fruits,  averaging  .264  to  .250  per  cent  of 
ash  in  the  whole  fruit,  while  prunes  averaged  .480;  plums, 
.535;  apricots,  .508;  oranges,  .432;  lemons,  .526;  cherries, 
.482;  and  grapes,  .500  per  cent  of  ash. 

The  ash  of  apples  averages  over  one-half  of  potash,  not 
unlike  the  other  fruits;  however,  the  analysis  shows  rather 
more  variation  for  ash  than  has  usually  been  noticed  in  the 
fruits  in  general.  The  same  remark  may  be  made  as  to 
variation  in  quantity  of  P2  O5,  the  next  largest  and  most 
important  ingredient.  But,  on  the  average,  this  amount  is 
found  to  be  much  like  that  in  the  ash  of  oranges,  figs,  and 
apricots,  which  contain  upwards  of  12  per  cent  of  phos- 
phoric acid;  as  against  21.24  per  cent  for  the  grape,  15.1 
for  cheny,  and  14.1  of  phosphoric  acid  for  the  prune. 
There  is  about  4  per  cent  lime  in  the  ash  of  apple,  and 
a  similar  amount  in  the  ash  of  cherries,  apricots,  prunes, 
and  grapes.  The  ash  of  oranges  and  lemons  contains  about 
five  times  as  much  as  that  of  the  apple. 

Colby,  in  speaking  of  fruits  grown  under  California  con- 
ditions, says,  "The  figures  found  for  apples  (and  pears) 
are,  on  the  whole,  so  much  smaller  than  those  which  have 
been  obtained  for  the  other  ordinary  orchard  fruits,  that  it 
would  seem  safe  to  conclude  that  here  fertilizers  will  not  be 
necessary  for  apple  crops  for  many  years  to  come.  However, 
the  figures  do  indicate  that  the  first  need  will  be  for  a  nitrog- 
enous fertilizer.  Along  with  this  need  will  come  that  for  a 
phosphatic  fertilizer.  There  is  no  reason  to  supply  potash  to 
apple  orchards  for  a  great  many  years  to  come. " 

4.  Forms  of  sugar  in  fruits. — There  is  not  absolute  uni- 
formity in  the  method  of  expressing  the  sugar-content 
of  fruits.  In  general,  however,  two  kinds  of  sugar  are 
present,  sucrose  and  invert  or  reducing  sugars.  The  sucrose 
is  mainly  cane-sugar  (C12H22O11),  while  the  invert  sugars  or 
dextrose   group    (C6H22O11)    consist   of   glucose    (dextrose), 


"6  POMOLOGY 

and  levulose  (fructose).  The  invert  sugars  are  formed 
during  the  ripening  process  of  fruits  and  result  from  the 
union  of  one  molecule  of  water  and  one  of  sucrose,  as  follows: 

Sucrose  Levulose  Dextrose 

C12H22O11+H2O  =  C6H12O6        +  C6H12O6 

Strictly  speaking,  invert  sugar  contains  equal  parts  tf 
levulose  and  dextrose,  as  can  be  seen  by  the  above  formula, 
while  reducing  sugars  include  levulose  or  dextrose  alone  or 
combined  in  varying  proportions,  and  may  include  other 
reducing  sugars  and  even  reducing  substances  not  sugars.^ 
This  situation  has  led  to  some  laxity  in  use  of  terms  and 
usually  the  sugars  are  stated  as  sucrose  and  invert  or  reducing 
sugars. 

5.  Sugar-content  of  ripe  fruit  juices. — Thompson  and 
Whittier  have  determined  the  percentage  of  sugars  in  ripe 
fruit  juices  by  means  of  polarized  light,  as  they  question  the 
value  of  determinations  made  by  specific  gravity  on  unknown 
solutions.  Their  work  showed  that  levulose  is  the  dominant 
sugar  in  apples,  pears,  quinces,  and  three  of  the  grapes,  and 
far  exceeds  the  dextrose  in  the  apples,  pears,  and  quinces. 
With  the  plum  and  one  variety  of  grape,  the  dextrose  exceeds 
the  levulose,  but  only  in  the  plum  does  it  far  exceed  it  and 
in  this  case  it  is  lower  than  the  sucrose.  Sucrose  is  the 
principal  sugar  in  peaches  and  plums. 

6.  The  essential  oils. — Power  and  Chesnut  ^  described 
the  oil  of  apples  as  follows:  "The  essential  oil,  as  extracted 
by  means  of  ether  from  a  concentrated  distillate  of  either 
ordinary  apple  parings  or  those  of  the  crab  apple,  is  at 
ordinary  temperatures  a  yellowish,  somewhat  viscid  liquid, 

1  Thompson,  F.,  and  A.  C.  Whittier.  Proc.  Soc.  Hort.  Sci.  1912. 
pp.  16-21. 

2  Power,  F.  B.,  and  V.  K.  Chesnut.    Jour.  Amer.  Chem.  Soc.  42:  No.  7. 


THE  COMPOSITION  OF  FRUITS  7 

becoming  much  darker  on  keeping.  When  shghtly  cooled  it 
forms  a  concrete  mass,  due  to  the  separation  of  small  ocicular 
crystals,  which  consist  of  a  paraffin  hydro-carbon.  It 
possesses  in  a  high  degree  the  characteristic,  fragrant  odor 
of  fresh  apples.  Besides  the  esters  mentioned,  it  has  been 
found  to  contain,  Ipy,  specific  tests,  small  amounts  of  ac- 
.  H^f  ^etaldehyde  and  furfural.  ■/ The  jaeld  of  oil  from  the  parings 
of  the  Ben  Davis  apple  was  0.0035  per  cent,  and  that  from 
the  more  odorous  crab  apple  0.0043  per  cent,  which  cor- 
responds to  about  0.0007  and  0.0013  per  cent  respectiv^ely  of 
the  entire  ripe  fruit. " 

The  esters  referred  to  above  are  "the  amyl  esters  of 
formic,  acetic,  and  caproic  acids,  with  a  veiy  small  amount 
of  the  capiylic  ester  and  a  considerable  proportion  of  ac- 
etaldehyde. " 

Amyl  valerate,  which  is  usually  referred  to  as  "apple  oil," 
has  not  been  identified  as  present  in  the  apple. 

7.  Quality  in  apples. — As  mentioned  above,  certain 
components  of  the  apple  give  it  flavor  or  eating  quality. 
The  term  is  used  rather  loosely  in  pomology,  referring 
sometimes  to  the  dessert  quality,  sometimes  to  the  cooking 
property,  and  again  to  shipping  and  market  quality. 

Shaw  ^  has  analyzed  apple  varieties  to  determine  the 
ingredients  which  are  associated  with  dessert  quality,  and 
the  two  apples  used  for  illustrating  high  and  low  quality  are 
the  Grimes  and  Ben  Davis.  The  following  figures  show 
the  relative  amounts  of  the  important  ingredients,  each 
being  the  average  of  eleven  determinations. 

1  Shaw,  J.  K.    Proc.  Amer.  Soc.  Hort.  Sci.    1912.    p.  29. 


j;5^^€HrtA^'"^    y^-i 


V    ^jy. 


POMOLOGY 


Table  V 

ANALYSIS   OF   A   HIGH    AND    A    LOW    QUALITY   APPLE    (AFTER   SHAw) 


Water 

Total 
solids 

Sol- 
uble 
solids 

Insol- 
uble 
solids 

Reduc- 
ing 
sugars 
invert 

Sucrose 

Total 
sugars 

Acid 

as 
malic 

Ben  Davis 
Grimes.  .  . 

84.32 

82.12 

15.66 

17.88 

12.59 
15.18 

3.07 
2.70 

6.91 

8.77 

2.95 
4.30 

9.86 
13.00 

.44 
.45 

From  these  figures  it  is  seen  that  the  high-quahty  apple 
has  a  much  larger  percentage  of  total  solids,  and  when  it  is 
remembered  that  upwards  of  75  per  cent  of  the  total  solids 
are  sugars,  it  will  be  seen  that  the  Grimes  is  much  to  be 
preferred.  (In  this  case,  the  Ben  Davis  has  about  62  per 
cent  and  the  Grimes  72  per  cent  of  sugar  in  the  total  solids.) 
While  sucrose  is  a  valuable  form  of  sugar  in  fruit,  it  has 
been  shown  previously  that  levulose  is  dominant  in  the  apple. 

The  relation  of  acid  to  sugar  is  important  for  high  quality, 
for  here  is  secured  the  sprightlincss  which  usually  is  associated 
with  a  dessert  apple,  although  this  depends  on  the  taste  of 
the  individual.  Shaw  found  from  .1  to  .2  per  cent  in  sweet 
apples  to  nearly  1  per  cent  or  possibly  more  in  very  acid 
sorts.  The  ratio  of  acid  to  total  sugars  varies  from  about 
one  to  one-hundredth  in  sweet  apples  to  one  to  eight-hun- 
dredths  in  very  acid  sorts. 

The  flavoring  or  essential  oils  which  have  been  discussed 
are  also  of  great  importance  in  quality, 

"It  appears  then  that  high  table  quality  in  apples  depends 
on  (1)  good  texture  which  is  accompanied  by  a  low  content 
of  insoluble  solids,  (2)  an  abundance  of  sugars,  especially 
sucrose,  (3)  an  amount  of  acid  sufficient  to  blend  agreeably 
with  the  sugars  but  not  excessive  and  (4)  an  abundance  of 
pleasant  and  agreeable  flavoring  oils. " 


THE  COMPOSITION  OF  FRUITS  9 

8.  The  effect  of  location  on  quality. — While  it  is  recog- 
nized that  there  is  a  niarketl  difference  in  quality  of  fruit 
depending  on  where  it  is  grown,  there  is  not  much  data 
showing  the  chemical  analysis  of  such  fruits.  Colby  ^  has 
shown  the  effect  of  location  on  quality  of  fruit,  particularly 
for  the  conditions  which  obtain  in  California. 

Apples  which  were  grown  at  a  high  elevation  averaged 
higher  in  both  sugars  and  acids,  which  makes  the  best 
combination  for  a  dessert  apple.  Those  raised  at  elevations 
(4000  to  5000  feet)  analyzed  as  high  as  15  per  cent  sugar  and 
.55  per  cent  acid  in  the  juice,  while  those  from  lower  levels 
(50-150  feet)  analyzed  about  2  to  4  per  cent  lower  in  sugars 
and  as  low  as  .16  and  .17  per  cent  acid  (in  terms  of  sulfuric 
acid,  SO3). 

Eastern  apples,  according  to  data  cited,  analyzed  from 
10.42  per  cent  sugar  (Baldwin)  to  11.36  per  cent  (Rhode 
Island  Greening)  in  the  juice.  European  grown  fruits 
showed  a  still  lower  sugar-content,  averaging  7.22  per  cent. 

9.  Composition  of  fruits  grown  on  irrigated  and  non- 
irrigated  land. — The  statement  has  not  infrequently  been 
made  that  fruits  grown  under  irrigation  are  "flat"  or  insipid 
in  flavor  and  are  less  able  to  withstand  shipment  and  rough 
handling  than  fruit  raised  on  non-irrigated  land.  To  deter- 
mine whether  there  is  any  essential  difference  in  composition, 
chemical  analyses  were  made  by  Jones  and  Colver  ^  of  various 
fruits  so  grown.  The  results  indicate  that  "From  a  general 
survey  of  analytical  results,  it  may  fairly  be  said  that  fruits 
in  general  manifest  a  well-defined  tendency  to  elaborate 
greater  percentages  of  total  solids  or  dry  matter,  conse- 
quently of  sugar,  acid,  and  crude  protein,  when  grown  in 
non-irrigated  sections.    With  comparatively  few  exceptions, 

1  Colby,  G.  E.    Rept.  Calif.  Agr.  Exp.  Sta.    1897-98.    p.  14.3. 
^  Jones,  J.  S.,  and  C.  W.  Colver.    The  composition  of  irrigated  and 
non-irrigated  fruits.    Idaho  Agr.  Exp.  Sta.  Bull.  75.     1912, 


10  POMOLOGY 

however,  no  marked  difference  between  irrigated  and  non- 
irrigated  fruits  in  actual  food  or  market  value  should  be 
charged  to  differences  in  composition." 

10.  Chemical  changes  in  the  growing  apple. ^ — Only  data 
for  winter  apples  will  be  included  here,  since  the  same  general 
processes  go  on  with  smnmer  varieties;  the  information, 
however,  is  not  so  satisfactory  owing  to  the  uneven  ripening 
of  the  latter. 

This  work  was  carried  on  with  Ben  Davis,  Huntsman,  and 
Winter  Paradise.  The  curves  (Fig.  1)  show  in  a  striking 
way  the  chemical  changes  which  occurred  throughout  the 
season,  from  June  16  until  November  5. 

Using  total  sohds  as  a  basis,  it  will  be  seen  that  starch 
increases  until  the  latter  part  of  July  when  it  has  reached  its 
maximum,  then  it  begins  to  decline  constantly  but  does  not 
entirely  disappear.  The  sucrose  curve  is  almost  the  exact 
reverse  of  the  starch.  This  form  of  sugar  starts  with  a  low 
percentage  and  continues  low  until  the  middle  or  latter  part 
of  July,  when,  through  the  conversion  of  starch  into  sugar,  it 
begins  to  rise  and  continues  until  the  fruit  is  ripe.  On  the 
date  of  the  first  examination  of  these  varieties,  June  16,  the 
content  of  sucrose  based  on  total  solids  was  4  per  cent,  and  at 
the  last  examination,  on  November  4,  it  amounted  to  25.4 
per  cent  of  the  total  solid  content  of  the  apple,  the  rate  of 
increase  being  apparently  no  greater  before  the  maximum 
content  of  the  starch  than  afterwards.  Unlike  the  smnmer 
apples  which  had  been  examined,  the  percentage  of  invert 
sugar  here  increased  from  the  date  of  the  first  examination  to 
approximately  the  date  of  the  last,  so  that  even  in  percentage 
composition  the  amount  of  invert  sugar  did  not  reach  its 
maximum  until  the  fruit  was  mature. 

In  all  three  of  the  varieties  of  winter  apples  studied,  the 

1  Data  and  comments  are  taken  from  work  of  Bigelow,  W.  D.,  H.  C. 
Gore,  and  B.  J.  Howard.    U.  S.  Dept.  Agr.  Bur.  Chem.  Bull.  94.     1905. 


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12  POMOLOGY 

percentage  of  malic  acid  decreased  from  the  first  examination 
to  the  full  maturity  of  the  fruit.  The  percentage  of  total 
sugar  estimated  as  invert  sugar  increased  steadily  from  the 
first  examination  to  full  maturity.  It  is  notable  that  after 
the  maximum  content  of  starch  is  reached,  the  percentage  of 
starch  and  invert  sugar  taken  together  remains  approxi- 
mately constant. 

More  recently  Thatcher^  has  shown  that  the  only  enzymes 
which  were  found  to  participate  in  the  changes  in  the  carbo- 
hydrates of  apples  during  the  ripening  process  were  the 
oxidases. 

11.  Composition  of  apples  in  common  storage. — It  is  of 
interest  to  follow  the  ripening  process  as  it  occurs  after  the 
fruit  is  picked  and  placed  in  storage.  The  work  of  Bigelow 
et  al.,"  Browne^  and  Kulisch,'*  are  in  substantial  agreement, 
although  performed  under  widely  differing  conditions. 

Bigelow's  work  with  Rhode  Island  Greening  apple  illus- 
trates this  ripening  process,  the  apples  having  been  picked 
between  October  6  and  November  7.  The  curves  in  Fig.  2 
show  graphically  the  progress  of  the  ripening.  By  referring 
to  them  it  will  be  noted  that  there  was  13  per  cent  of  sucrose 
on  August  25,  at  the  time  the  experiment  was  begun,  and  it 
increased  rapidly  until  November  7  when  it  reached  its 
maximum  30  per  cent.  The  sucrose  then  rapidly  disappeared 
until  February  11  when  the  experiment  was  discontinued,  at 
which  time  it  was  6  per  cent.  It  is  of  particular  interest  to 
note  that  the  starch  declined  rapidly  from  August  25  until 
November  7  when  it  entirely  disappeared,  this  being  the 
same  date  when  the  sucrose  reached  its  maximum.     Here 

1  Thatcher,  R.  W.      Enzyms  of  apples  and  their  relation  to  the  ripen- 
ing process.    Jour.  Agr.  Res.  5^:  1915: 103-116. 
^  Loc.  cit. 

^  Browne,  C.  A.,  Jr.      Penn.  State  Dept.  Agr.  Bull.  58. 
^Kulisch.S.     Landw.  Jahrb.  1892.    21:871. 


THE  COMPOSITION  OF  FRUITS 


13 


again  is  evidence 
that  the  starch  is 
transformed  into 
sugars  as  the  ripen- 
ing proceeds. 

The  malic  acid 
also  continues  to 
behave  as  it  did 
during  the  growth 
and  development  of 
the  fruit.  There  is 
a  gradual  disap- 
pearance through- 
out the  storage 
period. 

Invert  sugars, 
unlike  the  starch 
and  sucrose,  con- 
tinue to  increase 
throughout  the  ex- 
periment, being  as 
high  as  62  per  cent 
in  Februaiy.  They 
gain  rapidly  as  the 
sucrose  disappears, 
indicating  the 
transformation. 

The  total  content 
of  sugar  (calculated 

Fig.  2.— Curves  show- 
ing chemical  changes 
in  Rhode  Island 
Greening  apple  in 
common  storage. 


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14 


POMOLOGY 


as  invert  sugar)  increased  from  the  first  examination  to  the 
date  of  the  disappearance  of  the  starch.  After  this  date  the 
curve,  representing  the  total  sugar  as  invert,  merges  with 
that  indicating  the  total  carbohydrates  as  invert  sugar.  In 
the  Rhode  Island  Greening,  the  total  carbohydrate  content 
decreased  to  some  extent  after  the  disappearance  of  the 
starch.  This  latter  was  not  true,  however,  of  some  other 
varieties  studied. 

12.  Changes  in  composition  of  the  peach  during  growth 
and  ripening.^ — In  determining  the  chemical  changes  which 
take  place  in  the  growing  peach,  the  fruit  was  selected  at  the 
following  times  for  analysis:  (1)  after  the  June  drop,  (2)  when 
the  stone  hardens,  (3)  when  market  ripe,  and  (4)  when 
fully  ripe.  The  varieties  used  were  Triumph,  Rivers,  Early 
Crawford,  Stump,  Elberta,  Orange  Smock,  and  Heath  Cling. 

The  following  data  illustrate  the  marked  changes  in  com- 
position between  the  early  stages  of  growth  and  when  the 
peach  is  fully  ripe : 

Table  VI 

COMPOSITION  OF  PEACHES  AT  DIFFERENT  STAGES  OF  GROWTH 
COMPOSITION    OF    WHOLE    FRUIT    (AFTER    BIGELOW    AND    GORE) 


Average  of 
six  varieties 


Stage  of  growth 


June  drop 
Stone  hardened 
Market  ripe 


Weight 

of 
peach 


Grams 
9.51 
16.75 
73.59 


Per 

rent 
64.55 
71.54 
92.49 


Per 

cent 
32.50 
25.82 

6.86 


Per 
cent 
2.94 
2.89 
.65 


Total  solids  in 
flesh      stone    kernel 


Per. 

cent 
14.77 
16.97 
14.04 


Per 
cent 
9.37 
27 .  35 
66.94 


Per 

cent 


7.. 54 
44.78 


ANALYSI.S  OF  FLESH 

Stage  of  growth 

Sucrose  by 
reduction 

Reducing 

Acid  as 
sulfuric 

Ash 

Average  of 
six  varieties 

June  drop 
stone  hardened 
Market  ripe 

.18 
1 .  57 
5.70 

2.71 
2.26 
1.98 

.28 
.34 
.  56 

.75 
.68 
.40 

1  After  Bigelow,  W.  D.,  and  H.  C.  Gore.    U.  S.  Dept.  Agr.  Bur.  Chem. 
Bull.  97.     1905. 


THE  COMPOSITION  OF  FRUITS  15 

Between  the  time  of  the  June  drop  and  market  ripeness, 
the  peaches  increased  in  weight  nearly  eight  times.  During 
the  same  time  the  percentage  of  flesh  in  the  peach  in- 
creased less  than  one-half,  while  that  of  the  stone  decreased 
from  32.5  to  6.86  and  that  of  the  kernel  from  2.94  to  0.65 
per  cent. 

The  percentage  of  solids  of  the  flesh  remains  fairly  con- 
stant during  the  life  history  of  the  peach;  that  is,  the  increase 
in  solids  is  fairly  proportional  to  that  in  water.  This  is  shown 
by  the  fact  that  the  percentage  of  solids  did  not  greatly 
change  from  the  time  of  the  June  drop  to  the  period  at  which 
the  peaches  were  considered  market  ripe.  On  the  other  hand, 
in  the  same  period  the  stone  changed  greatly  m  its  nature. 
As  it  became  harder  and  more  mature,  the  percentage  of 
water  materially  decreased  and  that  of  solids  increased  from 
9.37  at  the  period  of  the  June  drop  to  66.94  when  the  peaches 
were  market  ripe.  The  solid  content  of  the  kernel  in- 
creased from  6.89  to  44.78  per  cent.  At  the  same  time,  it 
should  be  noted  that  the  percentage  of  solids  in  the  kernel 
did  not  materially  increase  until  after  the  hardening  of 
the  stone. 

By  examining  the  analysis  of  the  flesh,  it  will  be  seen  that, 
unlike  the  apple,  the  reducing  sugars  decreased  as  the  ripen- 
ing proceeded.  The  same  was  also  true  of  the  percentage 
of  nitrogenous  substances  in  all  their  forms  calculated  as 
total  protein,  albuminoids  and  amido  bodies,  and  also  of 
ash.  On  the  other  hand,  the  percentage  of  sucrose  and  of 
acids  increased  from  the  beginning  to  the  end  of  the  ex- 
periment. 

Analyses  were  also  made  to  determine  the  changes  which 
take  place  between  what  is  termed  "market  ripe"  and 
"full  ripe"  and  the  following  data  present  the  findings  dur- 
ing this  stage: 


16 


POMOLOGY 


Table  VII 

ANALYSIS  OF  FLESH  OF  THE  PEACH  (AFTER  BIGELOW  AND  GORE) 


/Su- 

Re- 

Total 

crose 

Marc  1 

ducing 

sugar 

bij  re- 

Acid 

sugar 

invert 

duction 

2.91 

2.20 

7.97 

6.23 

.53 

2.30 

2.27 

9.13 

7.36 

.48 

Ash 


Average . 


Market  ripe 
Full  ripe 


While  not  indicated  in  the  table,  there  was  not  much 
change  in  the  percentage  of  flesh,  stone,  and  kernel.  There  is 
some  increase  in  the  percentage  of  sugar,  while  that  of  marc 
and  acid  decreased  slightly.  It  may  also  be  pointed  out  that, 
comparing  the  composition  of  the  flesh  of  the  peach  with 
that  of  the  apple,  there  is  practically  no  starch  in  the  former 
(only  at  the  veiy  beginning),  while  the  latter  is  quite  high 
in  starch  until  later  in  its  development. 

13.  Ripening  process  in  pears. — The  pear  is  unique  in  its 
requirements  for  proper  ripening.  While  many  other  fruits 
may  be  picked  when  ready  for  use  or  when  "hard"  ripe  in 
order  to  lengthen  their  keeping,  the  pear  must  be  picked 
much  earlier  relatively  in  order  to  allow  the  ripening  process 
to  proceed  off  the  tree.  This  produces  a  fruit  of  much  higher 
quality  for  all  purposes  than  when  it  ripens  entirely  on  the 
tree.  Hence  a  study  of  the  changes  which  occur  in  ripening 
is  of  more  than  ordinaiy  interest,  and  the  work  of  Magness  ^ 
may  be  cited  in  this  connection. 

Fruit  which  had  been  produced  in  three  of  the  principal 
pear-growing  sections  of  the  Pacific  Coast  and  picked  at 

^  This  term  applies  to  the  total  insoluble  matter  of  the  flesh  of  the 
peach,  including  the  skin. 

2  Magness,  J.  R.  Investigations  in  the  ripening  and  storage  of  Bart- 
lett  pears.    Jour.  Agr.  Res.  19:  473-500.    8  fig.  1920. 


THE  COMPOSITION  OF  FRUITS  17 

intervals  from  early  summer  until  after  the  commercial 
picking  season,  were  analyzed  within  a  few  days  after  pick- 
ing and  after  being  in  storage  one  and  one-half  to  three  and 
one-half  months  at  temperatures  of  70,  40,  and  30  degrees  F. 
Both  sugars  and  acids  were  determined  as  well  as  the  alco- 
hol-insoluble, acid-hydrolyzable  reducing  materials. 

Like  the  apple  which  has  already  been  studied,  the  Bartlett 
pear  increased  in  total  sugar  from  early  suimner  until  after 
the  close  of  the  commercial  picking  season.  The  increase 
in  the  latter  part  of  the  season  is  mainly  due  to  an  accumu- 
lation of  sucrose,  while  the  earlier  increase  is  due  mainly  to 
reducing  sugar.  It  will  be  remembered  that  the  winter  apples 
showed  their  greatest  increase  in  sucrose  also  during  the  latter 
part  of  their  development,  although  the  invert  sugars  in- 
creased in  the  apple  throughout  the  ripening  process  of  the 
fruit. 

Further,  "A  distinct  relationship  was  found  between  the 
total  amount  of  sugar  present  in  the  ripe  fruit  and  the  tem- 
perature of  the  storage  at  which  it  had  been  held  from  the 
time  of  removing  from  the  tree  until  ripe.  Pears  ripened  at 
70°  F.  contained  the  highc^st  percentage  of  sugar;  those 
ripened  at  40°  possessed  the  lowest  total  sugar  content,  and 
those  held  at  30°  for  from  6  to  14  weeks  and  then  ripened  at 
room  temperature  were  intermediate  in  amount  of  total 
sugar.  There  was  no  marked  relation  between  temperature 
of  storage  and  relative  amount  of  sucrose  and  reducing 
sugar." 

It  is  further  observed  that,  "  It  seems  well  established, 
therefore,  that  the  highest  amount  of  sugar  will  be  secured  by 
holding  the  fruit  at  optimum  temperature  for  ripening. 

"Percentage  of  titratable  acid  in  the  fruit  tended  to  de- 
crease in  fruit  from  the  California  sections  as  the  season 
advanced,  while  it  tended  to  increase  in  that  from  Oregon 
and  Washington.    There  was  an  increase  in  acid  between  the 


18  POMOLOGY 

time  of  picking  and  the  time  of  full  ripening  of  the  fruit  when 
held  at  70°  F.  There  was  much  less  acid  in  fruit  ripened  at 
40°  than  in  that  ripened  at  70°,  and  still  less  in  fruit  that  had 
been  held  at  30°.  The  acid  content  of  fruit  that  was  allowed 
to  become  well  matured  on  the  tree  remained  nearly  con- 
stant during  storage."  Since  there  was  always  a  greater 
amount  of  acid  in  fruit  which  was  removed  and  ripened  at 
70°  F.  than  when  the  fruit  was  picked  from  the  tree,  it  be- 
comes "  of  interest  especially  in  connection  with  the  question 
of  whether  fruit  acids  are  synthesized  in  the  fruit  itself  or 
whether  they  are  carried  to  the  fruit  from  the  leaves.  The 
fact  that  there  is  an  increase  in  the  acid  between  the  time  the 
fruit  is  removed  from  the  tree  and  the  time  of  its  becoming 
ripe  is  evidence  that  there  is  an  actual  synthesis  of  acid 
in  the  fruit  itself. 

"There  was  a  progressive  reduction  in  the  alcohol-insol- 
uble, acid-hydrolyzable  reducing  material  as  the  season 
advanced,  not  only  in  the  fruit  fresh  from  the  tree,  but  also 
in  the  same  fruit  after  ripening.  There  is  a  marked  reduction 
in  these  substances  between  the  time  when  the  fruit  is  first 
picked  and  the  time  when  the  same  fruit  becomes  ripe. 

"The  percentage  of  total  solids  is  lowest  at  about  the 
opening  of  the  commercial  season.  This  tends  to  increase 
with  the  accumulation  of  sugar  in  the  late-picked  lots." 


CHAPTER  II 
THE  BUDS  OF  FRUIT-TREES 

An  accurate  knowledge  of  the  "bud  system"  of  the 
several  kinds  of  fruit-trees  is  of  first  importance  and  should 
be  thoroughly  understood  by  the  student  before  attempting 
to  leam  the  art  and  principles  of  pruning.  The  intelligent 
fruit-grower  observes  the  "set"  of  fruit-buds  and  their 
condition  as  a  guide  to  the  response  of  the  trees  to  cultural 
treatment;  he  likewise  examines  them  in  the  more  tender 
varieties  to  determine  the  percentage  of  live  buds  in  early 
spring.  Similarly,  in  many  other  ways  the  buds  afford  an 
index  to  the  functioning  of  the  tree. 

The  consideration  of  buds  naturally  divides  itself  into 
three  phases:  (1)  the  location  of  the  buds  on  the  tree,  and  the 
"bud  system"  in  the  different  kinds  of  fruits;  (2)  the  time 
and  details  of  differentiation  of  the  flower-buds;  and  (3)  the 
factors  that  influence  the  formation  of  flower-buds. 

Although  the  study  of  the  location  of  the  buds  on  the  tree 
is  no  longer  a  matter  of  intricate  research,  yet  it  requires 
accurate  observation  in  the  field  or  laboratory,  for  there  is 
much  still  to  be  learned  concerning  the  relative  economic 
value  of  buds  located  or  developed  in  different  parts  of  the 
tree,  or  of  a  branch  or  spur  system.  For  example,  it  has 
been  observed  that  in  some  varieties  of  the  peach  and 
cheny,  the  fruit-buds  are  more  hardy  when  they  are  borne  on 
short  growths  which  are  located  throughout  the  inner  area 
of  the  tree,  while  in  others  the  reverse  seems  to  be  true. 
Buds  in  certain  positions  also  are  more  likely  to  mature 
and  the  fruits  will  color  better  or  have  other  advantages 
over  those  borne  elsewhere  on  the  tree. 
19 


20  POMOLOGY 

14.  Buds  defined. — Buds  are  undeveloped  shoots  or 
branches,  whether  their  content  be  of  a  leafy  or  floral  nature 
or  both.  The  closed,  scaly,  resting  buds  of  fruit-trees 
represent  a  provision  of  the  plant  to  protect  the  tender 
growing  points  or  partially  developed  flowers  and  carry 
them  over  a  relatively  inactive  period.  This  provision  is  in 
contrast  to  the  "naked"  buds  of  many  tropical  trees  and 
shrubs,  where  climatic  conditions  do  not  require  a  winter 
resting  period,  and  yet  even  in  the  tropical  plants  a  period  of 
rest  of  greater  or  less  duration  does  exist.  It  might  be 
added  here  also  that  sometimes  there  are  several  such  periods 
of  rest,  followed  by  activity,  known  often  as  "flushes" 
of  growth.  Some  northern  plants  also  produce  naked  buds 
(as  niost  herbs,  Kalmia,  etc.).  Buds  have  also  been  de- 
scribed as  the  free  extremities  of  branches  or  incipient 
branches.^ 

15.  Gross  structure. — The  buds  of  all  the  common  fruits 
are  covered  with  overlapping  scales  which  are,  morphologi- 
cally, specialized  leaves.  The  bud-scales  are  accompanied  in 
some  cases  with  a  mat  of  soft  hairs  (pubescence)  and  some- 
times with  more  or  less  resinous  material  of  a  water-proof 
nature.  Within  these  scales  are  the  partially  developed 
leaves,  flowers  or  both,  depending  on  the  bud  in  question, 
and  the  axis  on  which  they  are  borne.  From  the  time  the 
buds  are  initiated  in  the  summer  (or  autumn)  previous,  until 
they  open,  there  is  a  progressive  development,  some  activity 
going  on  even  during  the  milder  weather  of  midwinter. 
Frequently  the  exact  number  of  leaves  which  a  shoot  will 
bear  are  present  in  the  bud,  but  this  is  not  always  the  case, 
for  vigorous  shoots  may  develop  additional  ones  during  the 
season.  Particularly  is  this  true  with  the  peach,  plum,  and 
apricot,  and  probably  to  some  extent  with  most  fruit-trees. 
Likewise  the  size  which  the  leaves  will  attain  is  determined 

1  Halsted,  B.  D.   Memoirs:  Torrey  Bot.  Club,  2:  Sept.  1890. 


THE  BUDS  OF  FRUIT-TREES  21 

by  the  "growing  conditions"  of  the  season  in  which  they 
expand,  and  the  reserves  carried  over  from  the  previous 
years.  However,  an  increased  length  of  shoots  may  be  due 
to  an  elongation  of  the  intemodes,  such  as  occurs  when  a 
tree  is  stimulated  just  previous  to  or  while  the  growth  is 
being  made,  or  if  the  tree  is  shaded  during  the  period  of 
growth  (the  latter  constituting  a  lack  of  light  stimulus). 

16.  Classification  of  buds.— Unfortunately  there  is  some 
conf\ision  in  the  terminology  relative  to  the  classification 
of  buds.  This  variance  in  nomenclature  by  horticultural 
writers  is  due  to  an  effort  to  use  terms  that  are  self-explana- 
toiy,  relating  to  position  of  the  bud,  its  structural  contents, 
or  to  what  it  will  give  rise.  The  following  terms  as  here  de- 
fined will  1)0  used  throughout  this  discussion. 

17.  Leaf-buds. — A  "leaf-bud"  contains  the  rudiments 
of  a  leafy  branch,  which  may  develop  into  a  shoot  or  a  spur. 
As  pointed  out  above,  the  development  of  parts  within  the 
leaf-bud  does  not  necessarily  predetermine  the  length  of  the 
shoot  or  the  number  of  leaves  it  will  bear.  Probably  such 
is  the  case,  however,  with  the  short  spurs.  The  term 
"branch"  bud  is  frequently  employed  in  horticultural 
writings  to  describe  the  same  type  of  bud  and  has  some 
advantages  in  clarity,  but  is  scarcely  more  accurate  than 
"leaf"  bud.  "Wood"  bud  is  also  used  by  some  writers,  but 
is  less  desirable  and  still  less  descriptive. 

18.  Fruit-buds. — A  fruit-bud  contains  the  unexpanded 
parts  of  the  flowers.  The  term  "inflorescence  bud"  would 
be  more  descriptive  but  does  not  follow  usage.  It  may  com- 
prise one  or  more  individual  flowers  and  perhaps  also  leaves  or 
bracts,  depending  on  the  kind  of  fruit-tree.  In  the  apple 
and  pear,  the  fruit-bud  usually  contains  one  or  more  axillary 
leaf-buds  also  as  well  as  the  enfolding  leaves.  That  is,  the 
blossom  buds  of  these  fruits  are  "mixed,"  and  when  they  have 
opened  and  fully  expanded,  a  close  examination  usually  re- 


22 


POMOLOGY 


veals  a  "secondary"  growth  arising  from  the  axil  of  one  or 
more  of  the  leaves.  This  secondary  growth  may  develop  into 
a  shoot  of  several  inches  in  length  or  into  a  spur;  generally 
it  is  short,  often- 
times merely  a 
bud.  Usually  it 
is  terminated  by 
a  leaf -bud,  but 
if  the  blossoms 
fail  to  "set,"  a 
fruit-bud  is  often 
formed.  In  fact, 
it  is  by  no  means 
rare  for  a  fruit-bud  to  form 
on  this  shoot  even  though 
one  or  more  fruits  are  de- 
veloping.    (See  Fig.  3.) 

19.  Flower-buds.— A 
flower-bud   is  one   of   the 
individuals  of  the  flower- 
cluster,  inside  or  outside  of  the  fruit- 
bud. 

20.  Simple  buds. — A  simple  bud 
contains  either  the  unexpanded  leaves 
or  flowers,  but  not  both.  The  term 
usually  refers,  however,  to  the  fruit- 
bud.  The  peach,  plum,  and  cherry  have  simple  buds,  but 
the  latter  may  contain  rather  prominent  leafy  bracts  also. 

21.  Mixed  buds. — A  mixed  bud  contains  both  flowers 
and  leaves;  hence  it  always  refers  to  the  fruit-bud.  The 
apple  and  pear  have  mixed  buds.  The  fruit-buds  of  the 
apple  and  pear  are  usually  larger,  plumper,  and  less  pointed 
than  the  leaf-buds,  but  this  is  by  no  means  universal.  In 
the  Baldwin  and  many  other  apples,  for  example,  it  is  almost 


Fig.  3.-Fruit  pro- 
duction and  two 
axillary  shoots, 
all  arising  from 
a  single  fruit- 
bud.     (Rome.) 


THE  BUDS  OF  FRUIT-TREES  23 

if  not  quite  impossible  to  distinguish  the  fruit-buds  in  the 
winter  without  dissecting  them.  Also,  different  varieties 
have  to  some  extent  fruit-buds  which  are  characteristic  in 
some  particular,  such  as  color,  shape,  size,  or  the  degree  to 
which  they  are  appressed  to  the  shoot. 

22.  Terminal  and  lateral  buds. — All  buds  of  necessity 
must  be  bonie  either  terminally  on  the  end  of  a  shoot,  in 
which  case  they  are  called  "terminal"  (or  apical),  or  on  the 
sides  of  the  shoot,  when  they  are  known  as  "lateral  buds." 
The  latter  regularly  occur  within  the  axil  of  a  leaf  and  are 
termed  "axillaiy  buds,"  although  at  times  some  lateral 
buds  are  adventitious.  If  more  than  one  leaf-scar  is  found 
at  the  base  of  a  bud,  it  must  be  considered  terminal  though 
on  an  exceedingly  short  shoot,  and  not  an  axillary  bud. 
Frequently,  a  very  close  examination  is  necessary  to  dis- 
tinguish between  an  axillary  and  a  terminal  bud  on  an 
exceedingly  short  spur.  On  the  other  hand,  not  all  buds 
which  appear  to  terminate  a  shoot  or  branch  are  terminal, 
for,  as  in  the  case  of  many  plums  and  the  apricot,  no  true 
terminal  bud  is  formed  but  the  distal  bud  is  axillaiy. 

23.  Latent  buds. — A  latent  bud  may  remain  dormant,  or 
fail  to  expand,  for  more  than  one  year  and  then  through 
some  impetus  or  stimulation  start  into  growth.  There  are 
a  large  number  of  latent  buds  on  fruit-trees,  and  if  this 
were  not  true  so  many  shoots  would  develop  that  many 
would  perish  for  lack  of  light,  nutrition,  and  other  factors. 
Often  these  donnant  or  latent  buds  are  overgrown  or  out- 
grown by  the  surrounding  tissues,  but  remain  alive.  Thus, 
many  apparently  adventitious  shoots  really  arise  from 
latent  buds. 

24.  Adventitious  buds,  as  mentioned  above,  arise  in  ab- 
normal or  unusual  places.  They  arise  on  both  roots  and 
branches,  especially  if  the  parts  above  are  removed  or 
injured.     After  severe  pnming  operations,  it  is  a  common 


24A  POMOLOGY 

^jSci^ence  for  adventitious  buds  to  arise  from  the  smooth 
T)afe  of  the  large  limbs  below  or  from  the  healing  tissue  about 
wound.  It  is  also  common  for  such  buds  to  form  and 
evelop  branches  below  a  ringed  portion  of  the  trunk  or 
limb. 

25.  Collateral  buds. — Buds  may  occur  singly  or  in  groups 
of  two,  three,  or  more  side  by  side,  in  which  latter  case  they 
are  said  to  be  collateral,  as  with  the  peach  and  some  kinds 
of  plums. 

26.  Leaf-scars  are  of  some  importance  in  studying  buds. 
The}^  are  the  former  places  of  attachment  of  the  leaves  and 
should  be  distinguished  from  those  of  the  bud-scales,  as  the 
latter  scars  are  sometimes  rather  conspicuous  early  in  the 
growing  season.  In  the  larger  leaf-scars  of  the  apple,  the 
points  of  separation  of  three  vascular  bundles  can  be  seen. 
As  an  axillaiy  fruit-bud  opens,  a  cleavage  plane  or  "crack" 
usually  occurs  in  the  tissue  between  the  vascular  bundles, 
but  this  should  not  deceive  the  observer  into  believing  each 
bundle  to  represent  a  separate  leaf-scar. 

27.  Fruit-spurs. — The  term  "fruit-spur"  as  commonly 
used  in  pomological  literature  designates  a  short  shoot 
that  produces  flowers  and  fruit,  in  contradistinction  to  the 
longer  shoots  of  the  tree.  Probably  no  clear-cut  distinc- 
tion can  be  drawn  between  these  spurs  and  the  other  vege- 
tative growths  of  the  tree,  since  a  fruit-spur  may  become 
highly  vegetative  and  develop  into  a  large  branch.  Like- 
wise also  a  short  growth  or  spur  may  continue  growth  for 
many  years  without  producing  flowers  or  fruits.  The 
general  term  "spur,"  however,  is  of  service  to  distinguish 
the  short  growths  which  are  common  on  fruit-trees  and  upon 
which  much  of  the  fruit  is  borne.  In  the  cases  of  the  plum, 
the  cheriy,  and  the  peach,  when  they  produce  spurs,  the 
fruit-buds  are  bonie  laterally,  whereas  the  terminal  or  distal 
bud  of  the  spur  generally  is  a  leaf-bud,  and  the  elongation  of 


THE  BUDS  OF  FRUIT-TREES 


25 


the  spur  is,  therefore,  continued  in  a  straight  line,  of- some- 
times the  spur  perishes  entirely.  With  the  apple  and  the  pear, 
on  the  other  hand, 
a  leaf-bud  may ! 
end  the  growing 
axis,  in  which  case 
further  elongation 
in  a  straight  line  is 
possible.  But  when 
fruit-buds  are  pro- 
duced they  are 
usually  terminal, 
whether  the  axis 
which  bears  them 
is  long  or  short,  so 
that  further  elon- 
gation of  the  spur 
is  forced  out  of 
a  straight  line 
through  the  devel- 
opment of  lateral 
buds,  which  may 
be  produced  below 
the  fruit-bud,  but 
as  a  rule  are  devel- 
oped from  axillaiy 
leaf -buds  which 
have  their  origins 
within  the  fruit- 
bud  itself,  as  is  discussed  above, 
short  or  several  inches  long. 

This  secondary  growth  is  of  prime  importance  in  the 
maintenance  of  the  fruit-spur,  although  when  the  spur  is 
very  weak  it  may  not  develop.     The  power  of  continuing 


Fig.  4. — Short  spurs  of  apple  bearing  termi- 
nal fruit-buds.     TF  =  terminal  fruit-bud. 


Such  growths  may   be 


26  POMOLOGY 

growth  or  development  in  the  short  spur,  especially  after 
it  becomes  old,  is  apparently  centered  largely  in  the  terminal 
bud,  whether  this  is  a  leaf-  or  flower-bud.^ 

28.  Fruiting  of  the  apple. — The  development  of  spurs  in 
the  apple  can  be  seen  in  Fig.  4.  Several  are  already  short 
fruit-spurs  and  others  may  or  may  not  develop  from  the 
short  tenninal  spurs  which  have  produced  only  a  leaf-bud 
at  the  terminus.  In  this  case,  all  the  lateral  buds  and  the 
terminal  one  on  the  one-year  growth  are  leaf-buds;  on  the 
two-year  wood  there  are  four  fruit-  and  five  leaf-buds  shown 
in  the  drawing;  and  on  the  three-year  wood  are  four  fruit- 
and  two  leaf-buds,  indicating  that  none  of  them  behaved  in 
their  second  year  as  occurred  above,  for  no  flowers  were 
produced  on  the  spurs  before.  This,  then,  may  be  con- 
sidered one  type  of  fruit-spur  formation  on  the  apple. 
Since  they  are  yet  unbranched,  they  may  be  termed  "sim- 
ple spurs." 

In  Fig.  5  is  shown  a  second  type  of  fruiting  habit  of  the 
apple.  In  this  case,  the  one-year  wood  has  produced  both  a 
tenninal  and  axillary  (or  lateral)  fruit-buds.  They  can  be 
clearly  distinguished  by  their  size.  This  type  of  flowering 
is  very  connnon  with  the  apple  and  pear.  This  is  a  case  of 
fruit-bud  formation  without  a  spur  being  first  developed, 
for  only  one  leaf  subtended  these  buds  and  hence  they  are, 
by  definition,  axillaiy.  The  student  should  make  close 
observations,  however,  for  it  is  not  unusual  to  find  a  very- 
short  spur  (sessile)  on  the  one-year  wood,  having  produced 
only  two  or  three  leaves,  and  hence  a  fruit-bud  in  such  a 

'  The  author  observed  for  several  years  the  results  of  "disbudding" 
spurs  by  partridge  or  grouse  {Bonasa  umhellus,  L.).  The  terminal  buds 
of  the  short  spurs  were  broken  off  throughout  certain  trees  in  an  orchard 
and  the  question  arose  as  to  how  long  it  would  be  before  the  spurs  were 
again  sufficiently  developed  to  produce  fruit-buds.  The  results  were 
rather  uniform  in  that  about  80  per  cent  of  these  spurs  died. 


THE  BUDS  OF  FRUIT-TREES 


27 


case  in  the  strict  sense 
would  be  terminal  and  not 
axillaiy.  Some  varieties 
of  apples  yield  amiual 
crops,  because  the  fruit  in 
one  of  the  years  is  pro- 
duced  largely  from   axil- 


TF 


Fig.  6. — The  beginning  of  a  fruit-spur  system  in 
the  apple. 


TF 


Fig.  5. — Axillary  and  terminal  fruit  bud 
formation  in  the  apple.  TF  =  terminal 
fruit-bud;  AF  =  axillary  fruit-bud. 


lary  fruit- 
buds  on  the 
one-year  old 
wood.  Such 
varieties  as 
the  Jonathan, 
Wealthy,  and 


28 


POMOLOGY 


Missouri  Pippin  produce  axillary  fruit-buds  freely.  The 
short  spurs  in  Fig.  5  are  homologous  to  those  in  Fig.  4. 
A  third  type  or  rather  an  advanced  stage  of  spur  formation 
is  seen  in  Fig.  6.  In  this  case,  a  terminal  fruit- 
bud  was  formed  in  1918  and  two  secondary  shoots 
arose  in  1919  from  the  cluster  base  (a),  both  of 
which  produced  fruit-buds.  In  1920  the  fruit- 
buds  expanded  and  developed  a  cluster  base  at  b 
and  bb,  and  they  gave  rise  to  one  short  secondary 
growth  at  c  which  is  a  leaf -bud,  and  two  secondary 
growths  at  cc  and  c'c',  both  of  which  were  leaf- 
buds  although  from  their  size  they  might  have  been 
mistaken  for  fruit-buds.  Thus  there  is  the  be- 
ginning of  a  "compound  spur  system" 
(probably  a  fruit-spur  system) . 
The  Rome  Beauty  produces  a  large  num- 
Cn  ber  of  its  fruit-buds  tenninally,  i.  e.,  on  the 
ends  of  rather  long  shoots.  In  fact,  this 
is  the  characteristic  method  of  production 
in  that  variety.  Usually  the  same  spur 
would  not  fruit  annually, 
but  every  second  or  third 
year,  depending  on  the 
vigor  of  the  tree.  If  the  his- 
tory of  the  branches 
is  traced  back  on 
the  tree,  it  will  be  found  that  the 
branch  (or  spur  system)  con- 
FiG.7.— A  flower-  tinues  to  elongate  and  the  place 
cluster  base  where  the  flowers  or  fruits  were 
that  has  pro-  borne  is  gradually  overgrown  and  ^ 
tZ'lTl  the  branch  appears  straight,  ^,^  ,^_,^, 
long  shoot.  rather  than  angular  as  m  the  fruit-spur  system 
(Rome  apple.)  case  of  the  short  branched     of  the  apple. 


Tf 


THE  BUDS  OF  FRUIT-TREES 


29 


TF 


spur  system,  such  as  is  illustrated  in  Fig.  8.    In  Fig.  7  is 
seen  the  beginning  of  the  spur  systems  of  the  Rome. 

What  may  be  termed  a  typical  compound  spur  for  many 
apple  varieties  is  shown  in  Fig.  8.    Such  a 
spur  may  continue  bearing  fruit  from  its 
several  units  for  manj^  years. 

29.  Fruiting  of  the  pear. — This  fruit  is 
closely  related  to  the  apple  botanically  and 
it  forms  its  fruit-buds  in  much  the  same 
positions.  The  fruit-bud  is  usually  termi- 
nal on  a  spur,  although  terminal  ones  on 
long  shoots  or  even  water-sprouts  are  fairly  _  T 
common.  Fig.  9  shows  a  shoot  of  pear 
which  has  produced  a  terminal  fruit-bud 
and  three  axillary  ones,  while  in  Fig.  10  is 
seen  a  vigorous  fruit-spur  on  which  three 
terminal  fruit-buds  appear  and  also  one 
axillary. 

30.  Fruiting  of  the  peach. — The  peach 
differs  from  the  apple  and  pear  because 
fruit-buds  occur  freely  on  the  vigorous, 
often  much  branched,  one-year-old  wood, 
which  also  produces  the  vegetative  exten- 
sion of  the  tree.  It  will  be  remembered 
that  the  one-year-old  temiinal  shoots  of 
the  apple  yield  a  veiy  small  portion  of  the 
fruit-buds  only  and  very  frequently  none. 
The  lateral  shoots  on  the  one-year-old  wood 
of  the  peach  may  be  rather  short  (less  than  ^'^  o  _  a  -'ll 
one  to  three  inches  long)  and  because  of  fruit-bud  forma- 
their  length  may  be  termed  spurs.  Such  tion  in  the  pear, 
spurs  are  frequently  very  fruitful,  and  the 

fruit-buds  produced  on  them  may  be  more  hardy  than  those 
on  the  more  rampant  growth  of  other  branches  or  trees.    Also 


30 


POMOLOGY 


short  spur-like  growths  are  frequently  found  on  the  older 
branches  or  trunk  of  the  peach  tree.  These  spurs  arise  from 
latent  or  adventitious  buds,  frequently  at  the  place  where  a 
shoot  or  branch  has  died  or  been  removed.  These  spurs  are 
often  fruitful  and  may  perish  after  one  year's  growth  or  may 
continue  a  short  unbranched  growth  from  a  terminal  leaf -bud 


Fig.  10.— a  vig- 
orous fruit- 
spur  of  the 
pear. 


lS/6 

for  two,  three,  or 
more  years,  but 
usually  they  are 
not  long-lived. 

The  peach  fur- 
ther differs  from 
the  apple  and  pear 
in  the  number  of  buds  that  may  stand  at  a 
node.  Any  of  the  following  conditions  may 
be  found  at  a  node  on  the  one-year  wood  of 
the  peach,  and  sometimes  all  of  them  on  a 
single  shoot: 

1.  A  single  leaf -bud. 

2.  An  axillary  fruit-bud. 

3.  A  leaf-bud  and  fruit-bud  in  the  axil  of  a 

single  leaf. 

4.  Two  fruit-buds  with  a  leaf -bud  between 

them  or  to  one  side  of  them  in  the 
axil  of  a  single  leaf,   or  with  a  leaf 


Fig.  11.— Fruit- 
ing habit  of 
the  peach. 


THE  BUDS  OF  FRUIT-TREES  31 

subtending    each   bud,    or   on   a   very   short   sessile 
spur. 

5.  Two  fruit-buds  in  the  axil  of  a  single  leaf, 

6.  Three  fruit-buds  in  the  axil  of  a  single  leaf. 

7.  A  fruit-bud  between  two  leaf-buds. 

The  fruit-buds  of  the  peach  are  usually  large  in  comparison 
with  the  leaf-buds  and  are  also  pubescent.  They  are  simple, 
comprising  as  a  rule  only  one  flower-bud,  but  in  some  cases 
they  may  contain  two.  As  a  rule,  a  weak  or  short  branch 
bears  only  single  fruit-buds,  while  the  double  or  triple  ones 
are  bonie  mostly  on  the  stronger  growth.  A  branch  may  be 
so  strongly  vegetative,  however,  that  no  fruit-buds  are 
produced.  Fig.  11  illustrates  the  fruiting  wood  of  the 
peach. 

31.  Fniiting  of  the  cherry.^ — Like  the  other  stone-fruits, 
the  sweet  cherry  bears  from  axillaiy  fruit-buds.  They  are 
formed  both  on  the  terminal  growth,  more  particular!}^  near 
its  base,  and  on  short  spurs  which  are  found,  character- 
istically, on  the  older  wood.  The  terminal  buds  of  both 
branches  and  spurs  are  leaf-buds,  with  the  result  that  their 
growth  is  in  a  straight  line,  in  contrast  to  the  apple  and  pear. 
Whipple  states  that  the  sweet  cherry  spurs  will  be  alternat- 
ing in  their  bearing  if  the  trees  are  not  well  cared  for  and 
properly  pruned. 

The  sour  cherry  forms  its  fruit-buds  in  practically  the 
same  positions  as  does  the  sweet  cheriy.  At  times  all  the 
axillar}^  buds  on  the  new  growth  are  fruit-buds,  which  results 
in  a  naked  branch  the  following  season.  The  tenninal  ones, 
however,  are  leaf -buds  and  hence  they  continue  the  growth  of 
the  spurs  and  branches  and  furnish  a  leaf  area  to  support  the 
developing  fruit  below.  Fig.  12  shows  one  type  of  fruiting 
wood  of  the  sour  cheriy. 

1  Whipple,  O.  B.  The  pruning  of  stone  fruit  trees.  Better  Fruit. 
Nov.,  1917.     Pruning  the  sweet  cherry.    Better  Fruit,  Dec,  1918. 


32 


POMOLOGY 


32.  Fruiting  of  the  plum. — It  is  necessary  to  divide  the 
plums  into  groups  according  to  species,  as  follows:  Prunus 
domestica,   P.    salicina,    and    the    American    species.     All, 

however,  bear  only- 
simple     buds,     al- 
though bracts  may 
appear    when    the 
buds  open. 
The  Domestica  plums 
often   develop   a   well- 
defined  system  of  fruit- 
spurs  in  which  the  terminal 
bud  is  a  leaf-bud  (rarely  a 
fruit-bud) .      Fruit-buds      are 
axillary  both  on  the  one-year- 
old  terminal  growth  of  the  tree 
and  on  the  one-year- 
old  wood  of  the  spur. 
They  are  usually  borne 
singly,  but  it  is  not  uncommon 
to  find  two  or  perhaps  three 
coordinately  in  the  axil  of  a  sin- 
gle leaf.    The  bud  itself  may  con- 
tain one,  two,  or  three  flower-buds 
(the    number    being    somewhat 
characteristic    for    the    variety) 
which  may  open  before,  with,  or 
after    the    leaves    appear.     The 
spur  under  some  conditions  may 
terminate  in  a  thorn  rather  than 
in  a  leaf-bud. 

The  Japanese  plums,  Prunus  salicina,  produce  axillary 
fruit-buds  only.  They  are  borne  on  the  new  wood  either 
singly  or  in  pairs  with  a  leaf -bud  between  them,  or  in  clusters. 


Fig.  12.— Fruiting  habit  of  the 
sour  cherry.  A  strongly  veg- 
etative type. 


THE  BUDS  OF  FRUIT-TREES  33 

They  also  are  bonie  singly  or  in  clusters  on  short  spurs  on  the 
older  growth,  and  such  spurs  may  also  be  produced  on  the 
new  growth. 

The  American  species  of  plum  are  much  the  same  as  the 
P.  salicina  in  fruiting  habits. 

33.  Fruiting  of  the  apricot. — The  fruiting  habit  of  the 
apricot  is  practicallj^  the  same  as  that  of  the  peach.  The  fruit- 
buds  are  boilie  singly,  or  in  pairs  on  the  new  growth  with  a 
leaf-bud  between  them,  or  on  short  spurs  on  the  older  growth. 
There  is  no  true  terminal  bud,  but  what  appears  so  is  a  true 
lateral  bud  and  it  continues  the  growth  of  the  branch.  The 
cluster  of  fruit-buds  on  the  new  growth  is  bome  in  the 
axil  of  a  single  leaf  instead,  as  may  occur  at  times  with  the 
peach,  each  bud  in  the  axil  of  a  leaf.  Spurs  are  formed  more 
frequently  with  the  apricot  than  with  the  peach. 

34.  Fruiting  of  the  quince. — This  fruit  differs  from  the 
apple  in  the  behavior  of  its  over-wintering  fruit-buds,  in 
the  fact  that  the  terminal  bud  which  contains  the  flower 
makes  a  short  leafy  growth  of  one  to  several  inches  and  the 
simple  (or  single)  flower  is  then  unfolded.  The  fruit-buds  are 
usually  produced  on  short  shoots  (spurs)  which  become 
branched  somewhat  after  the  mamier  of  an  apple  spur. 
Axillaiy  flower-buds  may  also  occur  abundantly  on  the 
one-year-old  terminal  shoots. 

35.  Fruiting  of  the  grape. — This  fruit  also  produces  over- 
wintering mixed  buds  l)onie  laterally  on  canes  of  one  year. 
The  flowers  occur  from  lateral  buds  on  the  one-year  wood. 
"  All  species  except  Vitis  Lahrusca  average  two  inflorescences 
to  the  cane  but  the  last-named  species,  at  least  in  some  of  its 
subdivisions,  may  bear  from  three  to  six  inflorescences,  each 
of  course  in  the  place  of  a  tendril  opposite  a  leaf."    (Hedrick.) 


CHAPTER  III 
THE  DIFFERENTIATION  OF  FLOWER-BUDS 

Before  studying  the  factors  that  influence  the  formation 
of  flovver-butls  in  fruit-trees,  the  morphological  changes  which 
take  place  in  bud  formation  from  the  earliest  stages  to  com- 
pletion should  be  well  understood.  This  has  been  worked 
over  by  several  horticulturists^  and  descriptions  of  the  stages 
of  development  are  available  for  the  apple,  pear,  peach,  plum, 
cheriy,  and  some  other  fruits. 

It  has  long  been  recognized  that  in  the  deciduous  tree- 
fruits,  generally,  the  flower-buds  are  more  or  less  well  devel- 
oped the  season  previous  to  their  unfolding,  although  the 
details  of  their  formation  have  been  worked  out  but  recently. 
As  late  as  1899,  Goff  wrote,  "no  systematic  investigation 
seems  to  have  before  been  made  that  gives  us  any  definite 
knowledge  as  to  the  time  when  the  development  of  the 
flowers  actually  begins,  the  rate  at  which  it  progresses,  or 
the  period  through  which  it  continues,  in  any  of  our  fruit 
bearing  plants." 

The  broader  details  of  the  differentiation  and  develop- 
ment of  the  various  floral  structures  and  organs  have  been 
carefully  outlined  for  the  apple.  The  course  of  development 
is  similar  for  the  pear,  and  is  broadly  the  same  for  the  drupa- 
ceous tree-fruits,  except  that  in  the  latter  the  receptacle,  or 

1  Goff,  E.  S.  17th  and  18th  Ann.  Rept.  Wis.  Agr.  Exp.  Sta.  1899- 
1900.  Waldron,  L.  R.  N.  D.  Agr.  Exp.  Sta.  Rept.  10:  31-39.  1899. 
Quaintance,  A.  L.  Ga.  Agr.  Exp.  Sta.  Rept.  13:  349-351.  1900. 
Drinkard,  A.  W.  Ann.  Rept.  Va.  Poly.  Inst.  1909  and  1910.  Kraus, 
E.  J.  Ore.  Agr.  Exp.  Sta.  Res.  Bull.  1.  part  1.  1913.  Bradford,  F.  C. 
Ore.  Agr.  Exp.  Sta.  Res.  Bull.  1.  part  2.  1915. 
34 


THE  DIFFERENTIATION  OF  FLOWER-BUDS        35 

calyx-cup  as  it  is  sometimes  called,  and  the  carpel  or  carpels, 
are  not  so  intimately  united  during  development  as  they  are 
in  the  pomaceous  types.  While  there  is  considei-able  diver- 
sity in  morphology  among  the  various  wild  species,  the 
cultivated  varieties  are  readily  placed  in  one  group  or  the 
other.  The  apple,  therefore,  may  well  serve  as  a  basis  for 
following  out  the  sequence  of  developmental  changes  which 
take  place  in  the  differentiation  of  the  fruit-bud  and  floral 
parts  in  the  more  common  deciduous  tree-fruits. 

36.  The  apple. — Just  prior  to  the  differentiation  of  the 
parts  of  the  flower-bud,  it  is  not  possible  to  distinguish 
between  those  growing  points  from 
which  flower  primordia  will  be  de- 
veloped and  those  which  will  remain 
as  vegetative  growing  points.  Each 
shows  a  smooth  rounded  crown  of 
meristematic  tissue  more  or  less  in- 
closed by  the  beginnings  of  leaves  or 
bud-scales.  As  the  season  progresses, 

the  axis  from  which    a    flower-bud 

.,,    ,       ,  1      11      1  r       Fig.  13. — Floral  diagram 

will  develop  gradually  becomes  dis-  f  fh    •      i 

tinguishable   through  what  appears 

to  be  a  thickening  or  more  broadly  rounding  or  flattening- 

out  of  the  growing  apex  or  the  crown  (growing  point),  and 

soon  thereafter  the  contour  of  this  crown  becomes  slightly 

irregular  or  papillatcd,  due  to  several  new  growing  points 

becoming  organized,  which  now  proceed  to  develop  into  new 

axes  (the  individual  flower  primordia)  and  on  these  in  turn 

growing  points  give  rise  to  the  individual  floral  parts  and 

tissues.    The  development  of  the  floral  parts  is  acropetal, 

wliich  means  that  they  are  differentiated  in  the  same  sequence 

as  they  occur  in  the  fully  developed  flower.     (See  Fig.  13.) 

Thus  their  order  of  development  is  as  follows:  calyx  (sepals), 

corolla  (petals),  stamens  and  pistils  (carpels).    As  the  pistils 


36 


POMOLOGY 


develop,  the  ovarian  cavity  is  formed  and  upon  the  placentae 
of  the  latter  the  ovules  are  borne.     (Fig.  14.) 

As  the  tip  of  the  axis  enlarges,  the  protuberances  which 
arise  spirally  below  it  develop  into  individual  flowers,  al- 
though one  or  two  leaf-buds  are  also  differentiated  slightly 
below  the  lowermost  flower  of  the  cluster. 


Fig.  14. — Early  stages  of  fruit-bud  differentiation  in  the  apple,  a,  grow- 
ing axis;  b,  incipient  lateral  flower-bud;  c,  beginning  of  a  bract 
in  the  axil  of  which  a  flower-bud  may  develop;  d,  a  bract  or  leaf; 
e,  surrounding  bracts  and  bud  scales;/,  vascular  bundles;  g,  pith. 

The  further  development  of  an  individual  flower-bud  of  the 
group  may  be  considered  as  representative  of  the  others  in 
the  cluster.  When  the  central  flower-bud  is  readily  recogni- 
zable, it  appears  as  a  very  short,  stocky,  conical  mass,  the 
apex  of  which  is  flattened  except  at  the  center  where  there  is 
a  small  slightly  convex  elevation  or  knob,  much  as  indicated 
in  Fig.  15.  A  section  through  the  bud  would  reveal  a  region 
of  actively  dividing  cells  near  the  upper  surface,  especially 


THE  DIFFERENTIATION  OF  FLOWER-BUDS        37 

toward  the  outer  edge  and  a  short  way  down  the  sides  of  the 
cone  or  cyhnder-Uke  growth.  The  tissue  beneath  these 
embryonic  regions  is  differentiated  into  pith  cells  and  vas- 
cular bundles,  and  inclosing  all  is  the  epidermis. 

37.  Sepals. — A  rapid  multiplication  of  the  cells  at  the 
outer  edge  of  the  near  upper  surface  of  the  bud  results  in  the 
formation  of  a  slightly  elevated  ridge,  the  torus  or  receptacle. 
(See  Fig.  16.)    Growth  takes  place  more  rapidly  at  five  points 


ca\yx  priTTiordia 
eoLge  of 


Fig.  16. — Diagramma- 

FiG.     15.  —  Diagram  tic  representation  of 

indicating  positions  origin  of  calyx  pri- 

of  four  flower  pri-  mordia   on   edge   of 

mordia.  torus. 

about  equally  spaced  on  this  ridge,  and  thus  the  primordia 
of  the  sepals  are  begun. 

Because  of  the  increase  in  number  and  size  of  the  cells 
below  and  between  the  calyx  primordia,  the  torus  or  recep- 
tacle of  the  flower  continues  development,  particularly 
toward  the  outer  edge,  with  the  result  that  this  outer  portion 
is  arched  up  and  the  calyx-lobes  are  elevated  along  on  top  of 
it.  The  petals,  stamens,  and  carpels  arise  from  the  concave 
side  of  the  toi-us,  and  the  meristematic  tissue  out  of  which  the 
primordia  of  these  organs  are  finally  differentiated  exists  as  a 
sort  of  lining  beneath  the  epidermis  of  the  cup-like  torus. 
As  development  continues,  the  sepals  enlarge  and  become 
inclined  toward  one  another  at  the  apex,  until  they  interlap 
and  form  a  tent-like  structure  over  the  depression  below 
them.    When  the  period  of  winter  rest  arrives,  these  parts 


38  POMOLOGY 

are  structurally  the  most  advanced  of  any  within  the  flower- 
bud. 

38.  Petals. — Almost  as  soon  as  the  primordia  of  the  sepals 
are  formed,  those  of  the  petals  appear,  the  latter  in  a  cycle 
within  and  alternating  with  the  former.^  "Development  is 
less  rapid  than  in  the  case  of  the  sepals  but  each  outgrowth 
gradually  assumes  a  thin  scale-like  appearance,  more  or  less 
sickle-shaped  in  longitudinal  section,  and  narrowly  attached 
at  the  base.  Each  petal  finally  assumes  an  acute  angle  with 
the  calyx  and  together  they  roof  over  the  cup-shaped  torus." 

39.  Stamens. — -"  Directly  after,  or  in  some  instances  even 
at  the  same  time  that  the  primordia  of  the  petals  are  being 
laid  down,  those  for  the  stamens  appear.  They  occur  in 
three  cycles.  Those  of  the  outermost  cycle,  directly  within 
the  petals,  are  laid  down  first,  though  they  are  immediately 
followed  by  the  other  two,  in  fact  in  some  cases  all  three 
apparently  form  at  the  same  time  though  the  outermost 
cycle  always  develops  the  most  rapidly.  The  outermost 
cycle  arises  so  near  to  the  primordia  of  the  petals  that  in  some 
sections  they  appear  almost  if  not  quite  connected,  though  as 
a  rule  they  are  veiy  distinct.  This  cycle  consists  of  five  pairs 
of  primordia,  each  primordium  appearing  at  first  as  a  blunt, 
broad  protuberance  scarcely  to  be  distinguished  from  a  petal 
primordium.  The  middle  and  innermost  cycles  each  consist 
of  but  five  primordia.  It  is  a  difficult  matter  to  decide 
whether  there  are  actually  three  or  but  two  cycles  of  stamens 
inasmuch  as  the  two  inner  cycles  are  extremely  close  together. 
From  an  examination  of  many  sections  and  dissections, 
however,  the  conclusion  that  there  are  actually  three,  seems 
to  be  well  founded.  The  young  stamen  rapidly  assumes  a 
distinctly  bi-lobed  appearance;  the  basal  lobe  is  short  and 
slender  while  the  apical  broadens  out,  and  it  in  turn  becomes 

1  The  following  quotations  are  from  E.  J.  Kraus,  Ore.  Agr.  Exp.  Sta. 
Res.  Bull.  1,  part  1.     1913. 


.^K 

^1 

A 

E^'«^:^LiM^BK  t# 

i 

M 

i 

/ 

r 

^M^I^SOt'- 

®^ 

^ 

m. 

s 

L 

r 

^^^ 

^ 

^ 

f 

1 

ifs.^ 

N 

w 

^ 

^ 

:;^ 

f- 

1? 

<j( 

pffl 

^1 

% 

-^ 

% 

i      1 

i 

THE  DIFFERENTIATION  OF  FLOWER-BUDS       39 

distinctly  four-lobed,  each  lobe  representing  a  distinct 
microsporangiuni.  The  microsporangia  pass  the  winter  in 
the  mother  cell  stage.  Only  slight  changes  take  place  during 
the  early  part  of  the  winter  up  to  the  middle  of  Februaiy  or 
the  middle  of  March,  when  more  active  growth  again  takes 
place. 

''The  stamens  in  the  outer  cycle  are  borne  in  pairs  side 
by  side  at  an  acute  angle  to  the  sepals,  while  the  two  inner 
cycles  are  bonie  at  nearly  right  angles  to  the  calyx  lobes. 
Furthermore,  of  each  pair  of  stamens  in  the  outermost  cycle 
one  stands  at  either  side  the  middle  line  of  each  calyx  lobe, 
each  stamen  in  the  next  cycle  of  five  stands  opposite  each 
petal,  while  each  stamen  in  the  innermost  cycle  of  five  stands 
opposite  the  middle  axis  of  each  sepal,  thus  alternating  with 
the  middle  cj^cle  of  stamens  by  which  they  are  partially 
overlapped  in  the  bud.  The  outermost  series  stands  more  or 
less  erect  and  after  the  expansion  of  the  petals  are  the  first  to 
dehisce,  the  two  inner  cycles  remaining  incurved  and  bent 
down  for  a  varying  length  of  time,  depending  on  environ- 
mental conditions.  They  soon  l^ecome  erect,  however,  and 
shortly  thereafter  dehiscence  of  the  anthers  and  discharge 
of  pollen  occurs." 

40.  Carpels. — "The  five  primordia  for  the  carpels  are 
the  last  to  appear,  doing  so  inunediately  after  the  primordia 
of  the  proximal  cycle  of  stamens  have  been  laid  down.  They 
are  bome  immediately  within  the  innermost  cycle  of  stamens 
and  some  distance  from  the  center  of  the  torus,  which  is  now 
apparently  lower  than  the  outer  edges  which  have  been  under- 
going elevation  continuously;  the  torus,  accordingly,  has 
become  distinctly  cup  shaped  at  this  time. 

"The  primordia  of  the  carpels  like  all  other  structures 
previously  mentioned,  appear  first  as  short  blunt  protuber- 
ances arising  from  th(^  torus.  Directly  after  this  very  early 
beginning,  growth  does  not  proceed  equally  in  all  directions 


40  POMOLOGY 

from  the  center  and  form  a  solid  cone-like  or  spherical  struc- 
ture, but  instead,  about  the  circumference  of  a  circle  which  is 
not  quite  closed,  thus  forming  as  further  growth  takes  place, 
a  narrow  hood-like  scale  with  infolded  edges. 

''Actual  elevation  above  the  surface  of  the  torus  takes 
place  slowly  at  first;  but  growth  and  elevation  proceed  very 
rapidly  across  the  entire  remainder  of  the  torus  except  at  the 
center.  This  central  portion  becomes  elevated  very  slightly, 
however,  and  its  level  is  raised  a  trifle  above  the  level  of  the 
bases  of  the  concavities  of  the  several  carpels,  thus  resulting 
in  the  formation,  at  the  center  of  the  torus,  of  a  tube  or  cavity 
around  which  the  five  carpels  are  arranged,  their  inner  edges 
forming  the  wall  of  this  cavity.  .  .  .  Each  carpel  is  furnished 
with  two  placentae  which  are  the  result  of  the  infolding  of 
the  edges  of  the  caipels.  In  the  case  of  so-called  "open 
cored"  pomes  the  cavities  of  the  carpels  open  directly  into 
the  center  cavity  and  the  placentae  then  appear  to  be  parietal 
about  the  common  center.  The  ovaiy  becomes  one-loculed 
instead  of  five-loculed  and  the  placentae  of  adjoining  carpels 
are  more  intimately  connected  than  are  the  placentae  of  any 
single  carpel. 

"...  Later,  growth  of  the  carpel  takes  place  most 
rapidly  at  the  upper  surface  of  the  torus  involving  at  the 
same  time  a  portion  of  the  latter,  thus  resulting  in  the  elonga- 
tion of  the  five  styles  as  a  solid  column  at  some  distance  below 
their  apexes.  A  careful  examination  of  a  median  longitudinal 
section  through  the  fruit  and  styles  will  reveal  the  presence  of 
the  tissue  of  the  torus  extending  for  a  short  distance  up  the 
styles.  In  the  mature  fruit  of  many  varieties  these  united 
style  bases  persist  and  are  known  as  a  '  pistil  point  or  style 
point.'  Still  later  growth,  shortly  before  the  expansion  of 
the  flower,  produces  an  elongation  of  that  part  of  the  styles 
between  the  apex  (stigma)  and  the  united  portion.  .  .  .  The 
conductive  tissue  is  traceable  from  the  stigma,  at  which 


THE  DIFFERENTIATION  OF  FLOWER-BUDS       41 

point  it  is  not  covered  by  the  epidermis,  down  through  the 
style  into  the  placontsB  of  the  carpels  to  the  ovules. 

"There  are  no  traces  of  the  ovule  evident  at  the  beginning 
of  the  winter  rest,  nor  do  they  appear  until  active  growth  has 
been  resumed  in  the  spring.  A  small  protuberance,  slightly 
below  the  middle  of  the  carpel,  first  becomes  evident,  about 
the  time  the  winter  fruit  buds  are  swelling  and  almost 
munediately  a  second  blunter  protuberance  appears  directly 
below  it.  .  .  .  The  upper  protuberance  which  becomes  the 
ovule  develops  very  rapidly.  At  first  it  stands  at  nearly  right 
angles  to  the  placenta  from  which  it  arises.  Very  soon  there- 
after, as  growth  progresses,  it  begins  to  assume  a  slightly 
downward  and  outward  movement  away  from  the  middle 
line  of  the  carpel  toward  the  side  walls.  At  this  time  the 
initial  development  of  the  integuments,  of  which  there  are 
two,  begins.  They  develop  at  practically  the  same  time 
though  the  imier  may  be  slightly  in  advance  of  the  outer.  At 
this  time  the  axis  of  the  ovule  no  longer  remains  at  right 
angles  to  the  placenta,  but  now  forms  an  acute  angle  with  it, 
the  distal  end  of  the  ovule  pointing  do^vnward  and  outward 
toward  the  sides  of  the  carpels.  Thus  the  two  ovules  in 
each  locule  stand  back  to  back,  so  to  speak,  their  tips  point- 
ing toward  the  base  of  the  carpel.  At  the  time  the  flower 
is  in  full  bloom  the  integuments  entirely  cover  the  nucellus, 
the  ovule  has  become  completely  anatropous  and  the  micro- 
pylar  end  rests  against  the  obturator  below  it.  The  embiyo 
sac  and  its  contents  are  completely  formed  at  this  time  and 
are  ready  for  fertilization."    (See  Fig.  17.) 

41.  The  peach,  plum,  and  cherry. — The  peach  in  Virginia 
showed  initial  differentiation  of  flower-buds  during  the  first 
week  in  August.  The  plum  varied  more  than  other  fruits  in 
the  time  of  initial  development  of  the  flower-buds.  With 
the  Japanese  varieties,  it  was  the  second  week  in  July,  with 
those  of  the  American  group  it  was  the  first  week,  while  the 


42 


POMOLOGY 


American  variety  Whitaker  (P.  hortulana)  did  not  differenti- 
ate until  the  first  week  in  September.  Goff  showed  that  the 
plum  began  differentiation  in  Wisconsin  about  the  8th  of 
July.  The  cheriy  in  Virginia  gave  evidence  that  fruit-buds 
were  forming  the  first  week  in  July  and  the  flower  parts  had 
begun  to  differentiate  by  the  end  of  the  month.  Goff's 
observations  are  much  the  same,  placing  the  date  at  July  1 1th. 
42.  Inflorescence. — In  the  development  of  the  fruit- 
buds  as  described  above,  the  arrangement  of  the  individual 


Fig.  17. — Diagram  showing  development  of  the  apple. 


flowers  is  termed  the  inflorescence.  In  the  apple  (Pyrus 
Malus)  it  is  known  botanlcally  as  a  cyme,  which  by  defini- 
tion is  a  convex  or  flat  flower-cluster  of  the  determinate 
type,  the  central  or  terminal  flower  unfolding  first.  There  are 
times,  however,  when  several  of  the  central  flowers  open  at 
the  same  time  as  the  terminal  one,  and  sometimes  the  ter- 
minal one  is  abortive  and  does  not  open  at  all.  Black^  has 
shown  graphically  the  arrangement  of  the  flowers  on  the  axis 
of  the  apple.    The  terminal  one  is,  of  course,  without  a  sub- 

1  Black,  C.  A.    N.  H.  Agr.  Exp.  Sta.  Tech.  Bull.  10.    1916. 


THE  DIFFERENTIATION  OF  FLOWER-BUDS       43 


tending  bract  or  leaf,  while  the  upper  lateral  flowers  are  in 
the  axils  of  bracts  and  the  lower  ones  in  the  axils  of  leaves 
(or  sometimes  bracts  also).    (Fig.  18.) 

The  pear  (Pyrus  communis)  has  its  inflorescence  in  a 
cymose  raceme,  as  the  flowers  at  the  base  of  the  cluster 
often  open  first,  which  is  the  reverse  of  the 
apple.  The  quince  {Cydonia  ohlonga)  pro- 
duces solitary  flowers  which  are  either 
terminal  or  axillaiy.  In  the  apricot  the 
flowers  are  solitary  and  axillary;  in  the 
wild  black  cherry  (Prunus  serotina),  the 
inflorescence  is  a  raceme;  in  the  sweet  and 
sour  cherries  a  fascicled  umbel;  and  in 
Fig.  18.  —  Diagram- 
matic drawing  of  an 
apple  inflorescence 
or  peduncle  from 
which  arise  the 
pedicelled    flowers. 


e^etative 


the    peach   the  ^'^''^^1 
flowers    are    soli-  T^junde 
tary  and  axillary, 
as  a  rule. 

43.  The  flower- ,,^^^,,,^.. 
ing   branch. —  aiapRmarjc 
There  is  not  en- 
tire uniformity  as 
to  the  nomencla- 
ture of  the  parts 
of    the    flowering 
branch,     but    for 
horticultural   usage   the   following   terms   are   satisfactory. 
(Fig.  19.) 

Scale  axis. — This  part  of  the  flowering  branch  is  the  basal 


44  POMOLOGY 

portion  which  bears  the  bud-scales  and  which  is  generally  not 
conspicuous  but  can  always  be  made  out. 

Vegetative  axis. — This  term  designates  the  vegetative 
branch  produced  from  the  fruit-bud  and  upon  which  the 
individual  flower  or  flowers  are  borne.  It  is  especially  con- 
spicuous in  such  cases  as  the  quince,  raspberry,  and  black- 
berry. 

Cluster  base.- — A  type  or  specific  form  of  the  vegetative 
axis  which  remains  short  and  often  thickens  up  or  becomes 
somewhat  fleshy,  is  termed  the  cluster  base.  On  it  are  borne 
leaves,  flowers,  and  frequently  vegetative  buds  which  may 
remain  dormant,  become  fruit-buds,  or  push  out  into  vegeta- 
tive branches  of  greater  or  less  length  in  the  case  of  the 
pomaceous  fruits,  whereas  with  some  of  the  drupaceous  types 
it  may  bear  only  a  few  bracts  in  addition  to  the  flowers  and 
become  deciduous  after  the  fruit  has  matured  or  fallen.  In 
the  pear  it  may  become  very  much  enlarged  and  more  or 
less  fleshy. 

Peduncle  is  the  main  axis  of  an  inflorescence,  and  to  which 
the  pedicle  or  stem  of  the  fruit  is  attached.  In  the  apple  it  is 
very  short,  while  in  some  cherries,  e.  g.,  P.  virginiana,  it 
may  be  long. 

Pedicel  is  the  true  stem  of  the  individual  flower  and  be- 
comes the  stem  of  the  fruit. 

44.  Vascular  anatomy.^ — The  location  of  the  vascular 
tissues  throughout  the  fruit  is  important  to  the  pathologist 
and  entomologist  as  well  as  to  the  pomologist  and,  therefore, 
it  should  be  briefly  reviewed  in  this  connection.  The  general 
details  have  been  traced  in  the  Yellow  Newtown  apple  and 
this  variety  may  serve  in  general  for  others  of  this  fruit. 

Within  the  cluster  base  is  an  almost  complete  woody 
cylinder  of  vascular  elements,  and  from  this  cylinder  strands 

^  Details  of  this  treatment  follow  closely  after  E.  J.  Kraus  and  G.  S. 
Ralston.    Ore.  Agr.  Exp.  Sta.  Bull.  138.     1916. 


THE  DIFFERENTIATION  OF  FLOWER-BUDS       45 

or  fibers  extend  into  the  leaves,  branches,  and  bracts.  A 
similar  though  somewhat  smaller  vascular  cylinder  exists 
in  the  peduncle  and  from  it  vascular  elements  extend  into 
the  flowers,  leaves,  and  bracts  which  it  bears.  The  vascular 
cylinder  becomes  smaller  and  smaller  toward  the  apex  of 
the  peduncle,  so  that  at  the  base  of  the  terminal  flower 
pedicel  there  remains,  usually,  but  five  prominent  strands 
and  between  them  manj^  smaller  fibers.  These  five  main 
strands  continue  up  through  the  pedicel  to  well  above  the 
middle  or  toward  the  apex  where  each  bundle  is  divided  into 
two,  thus  forming  ten  primary  bundles.  The  smaller 
longitudinal  fibers,  together  with  others  which  branch  from 
the  primary  bundles,  extend  in  toward  the  longitudinal 
median  axis  of  the  pedicel.  A  secondary  cylinder  is  thus 
formed  within  the  primary  one.  Just  below  the  apex  of  the 
pedicel,  these  small  fibers  and  others  which  extend  from  the 
ten  large  bundles  previously  mentioned,  are  bent  inward 
toward  the  small  inner  cylinder  and  a  confused  branching 
and  anastomosing  of  all  the  smaller  bundles  occurs,  thus 
completely  eliminating  any  resemblance  to  a  circular  or 
cylindrical  arrangement  of  the  smaller  fibers  at  this  point. 
At  the  apex  of  the  pedicel,  the  ten  large  primary  bundles 
are  arranged  as  an  outer  and  inner  cj^cle,  each  of  which 
consists  of  five  bundles.  From  each  of  the  bundles  of  the 
outer  cycle,  a  prominent  bundle  extends  upward  and  follows 
the  dorsal  line  of  a  carpel.  In  all,  therefore,  fifteen  distinct 
bundles  and  a  complex  mass  of  small  fibers  extend  from  the 
pedicel  into  the  fleshy  portion  of  the  apple.  (See  Fig.  20.) 
The  ten  primary  bundles  which  diverge  at  the  apex  of  the 
pedicel  follow  closely  the  so-called  core-line  of  the  fruit 
which  has  been  shown  to  mark  the  boundary  between  the 
pith  and  cortical  tissues.  Each  of  the  main  bundles  of  the 
outer  cycle  extends  opposite  the  dorsal  suture  of  a  carpel; 
one  of  the  terminal  branches  ends  in  a  calyx-lobe,  the  other 


THE  DIFFERENTIATION  OF  FLOWER-BUDS       47 

in  one  of  the  stamens  of  the  innermost  cycle.  Each  of  the 
main  bundles  of  the  inner  c^'cle  alternates  with  a  carpel  and 
its  terminations  are  in  the  stamens  of  the  middle  and  outer 
cycle,  the  petal,  and  the  lobes  of  the  calyx.    Large  branches 


l\JB-\- 


FiG.  21. — Diagram  illustrating  distribution  of  bundles  in  the  torus  and 
pedical  apex.  Note  the  separation  of  carpellary  and  toral  sys- 
tems, the  region  of  anastomosis  below  the  carpels,  and  ending  of 
bundles,  {i  v  c)  inner  vascular  cylinder,  (o)  bundles  supplying  ovule, 
(p  c  b)  placental  carpellary  bundle,  (c)  carpel,  (s  c  h)  net  work  of 
secondary  carpellary  bundles,  {d  c  h)  dorsal  inner  primary  toral 
bundles,  (c  h)  secondary  cortical  bundles,  (s)  bundles  to  sepal, 
{sti  sti  stz)  bundles  to  first,  second  and  third  cycles  of  stamens, 
(p)  bundle  to  petal,  (p  dotted)  pit  region. 


from  all  of  these  main  bundles  also  extend  outward  into  the 
cortex,  where  they  are  subdivided  into  many  smaller  fibers 
which  anastomose  to  form  a  close  network  in  the  cortex. 
None  of  these  bundles  extends  into  the  pith.    (See  Fig.  21.) 


48  POMOLOGY 

45.  The  carpellary  system. — A  short  distance  above  the 
apex  of  the  pedicel,  the  carpellary  system  of  bundles  is 
entirely  distmct  from  that  of  the  toral  region.  It  consists 
mainly  of  fifteen  prominent  bundles,  three  for  each  carpel, 
and  the  smaller  bundles  which  anastomose  throughout  the 
carpellary  tissue.  This  system  is  derived  from  two  sources: 
first,  the  five  prominent  strands  already  noted,  each  of 
which  extends  from  an  outer  primary  toral  bundle,  along 
the  dorsal  line  of  each  carpel;  and  second,  the  numerous 
small  bundles  extending  out  of  the  region  of  anastomosis  at 
the  apex  of  the  pedicel  into  the  walls  of  each  of  the  carpels 
and  the  larger  strands  which  extend  both  from  the  strands 
of  the  inner  and  outer  vascular  cylinder  more  or  less  obliquely 
through  the  pith  and  into  the  placentae  of  each  carpel. 

46.  Comparative  morphology  of  fruits. — A  mature  fruit, 
as  used  in  pomology,  usually  consists  of  the  ripened  ovary 
or  ovaries  together  with  the  fleshy  edible  parts  which  are 
intimately  associated  with  the  seed  production.  In  the 
case  of  parthenocarpic  fruits,  however,  the  fleshy  portion 
develops  independently.  Botanically,  the  term  is  used  in  a 
broader  sense  and  is  described  as  an  ovary  and  its  contents 
together  with  any  closely  adhering  part.  The  structures 
which  enter  into  the  make-up  of  the  several  fruits  are 
distmctly  different  in  specific  cases  and  some  of  those 
commonly  met  with  in  pomology  will  be  mentioned. 

A  pome,  of  which  the  apple,  pear,  and  quince  are  examples, 
is  composed  of  more  than  one  ovary  located  within  the  core 
region,  and  the  enveloping  receptacle  which  is  the  edible 
portion  of  these  fruits.  Other  parts  are  also  attached  or 
associated  with  the  ones  mentioned,  as  the  pedicel,  the 
modified  pith  which  is  within  the  core-lines  and  attached  to 
the  ovary  walls,  the  calyx  which  usually  persists;  and  the 
dried  stamens  and  styles. 

A  drupe  consists  of  a  single  carpel,  one-celled  and  one- 


.  THE  DIFFERENTIATION  OF  FLOWER-BUDS       49 

seeded  (or  at  most  two-seeded),  in  the  ripening  of  which  the 
outer  portion  of  the  ovary  (pericarp)  often  becomes  fleshy  or 
pulpy  as  in  the  peach,  plum  and  cherry,  or  thinner  and  hull- 
like as  in  the  almond,  and  the  inner  portion  of  the  ovary 
becomes  stony  or  crustaceous;  hence  the  term  "stone-fruits." 

The  raspberry  consists  of  an  aggregate  of  drupelets  which 
develop  about  a  thickened  portion  of  the  torus  but  from 
which  they  readily  separate  as  they  mature.  The  drupelets 
may  adhere  closely  after  being  harvested  or  they  may  have 
a  tendency  to  crumble  apart,  depending  on  the  variety. 

The  blackberry  is  likewise  an  aggregate  of  drupelets  but 
it  differs  from  the  raspberry  in  that  the  drupelets  adhere  to 
the  fleshy  part  of  the  torus  and  the  entire  mass  usually 
separates  from  the  calyx  and  flattened  portion  of  the  torus 
when  mature.  The  loganberry  is  the  same  morphologically 
as  the  blackberry. 

The  strawberry,  like  the  fruits  just  described,  is  not  a 
true  berry.  It  consists  of  a  much  thickened  fleshy  and  edible 
portion  of  the  torus  or  receptacle,  upon  which  are  located 
the  true  carpels  which  are  hard  one-seeded  achenes  scattered 
over  the  surface  of  the  receptacle.  They  may  be  somewhat 
depressed  or  slightly  raised  and  the  styles  may  be  deciduous 
or  may  persist  and  give  the  surface  a  more  or  less  roughened 
surface.     The  persistent  calyx  is  leafy  and  prominent. 

A  berry  proper  is  an  indehiscent  fruit  fleshy  throughout. 
There  is  considerable  variation  in  the  details  of  the  con- 
struction of  the  berry.  Some  of  them,  such  as  the  blueberry, 
huckleberry,  cranberry,  and  banana,  are  inferior  ovaries, 
whereas  others,  such  as  the  tomato,  orange,  lemon,  and  other 
citrus  fruits,  are  superior  ovaries. 

In  the  nut  the  ovary  is  hardened  into  a  "shell "  and  it  is  fre- 
quently covered  or  surrounded  by  a  husk  which  consists  of  the 
perianth  of  the  flower  or  bracts  which  are  derived  from  the 
receptacle.    The  edible  portion  is  composed  of  the  embryo. 


CHAPTER  IV 

FACTORS  WHICH  INFLUENCE  FRUIT-BUD 
FORMATION 

The  time  of  the  formation  of  fruit-buds  in  the  more 
common  tree-fruits,  as  well  as  the  morphological  details  of 
development,  for  the  most  part  have  been  definitely  estab- 
lished as  indicated  in  the  previous  chapter.  However,  the 
physiological,  biochemical,  or  biological  factors  that  influence 
the  differentiation  of  the  elements  of  a  flower-bud  out  of 
the  growing  region  are  still  being  investigated.  The  com- 
mercial pomologist  is  greatly  concerned  with  the  regular 
flowering  and  fruiting  of  trees,  but  unfortunately  the  litera- 
ture on  this  phase  of  the  problem  seems  to  have  been  widely 
mfluenced  by  tradition  and  as  a  result  many  more  or  less 
fanciful  theories  have  gamed  some  prominence.  Much 
confusion  would  be  avoided  if  the  facts  were  kept  to  the 
fore  that:  (1)  several  factors  may  limit  the  formation  of 
fruit-buds,  and  the  expression  of  these  may  be  entirely 
different  under  varying  conditions;  and  (2)  that  widely 
different  horticultural  practices  or  operations  may  influence 
such  factors  similarly  or  variously,  with  the  result  that  the 
conditions  for  the  formation  of  fruit-buds  may  be  either 
favored  or  suppressed.  The  considerations  which  follow 
have  to  do  with  practices  which  influence,  and  theories 
which  pertain  to,  fruit-bud  formation. 

47.  Vegetative  and  reproductive  processes. — Fruit-trees 
manifest  growth  of  two  rather  distinct  kinds — that  primarily 
associated  with  simple  vegetative  extension  and  that  more 
closely  tied  up  with  reproductive  processes  or  functions. 
It  has  been  a  common  notion  that  they  are  not  only  distinct 
50 


FRUIT-BUD  FORMATION  51 

in  manifestation  but  antagonistic  in  nature.  This  position, 
however,  is  scarcely  tenable  because  the  so-called  fruit-spurs 
and  buds  and  even  many  of  the  fruits  themselves  are,  in 
their  first  inception  and  development,  as  truly  vegetative  as 
the  new  shoots  and  branches.  It  is  a  fact,  however,  that 
under  extreme  conditions  of  vegetative  extension,  little  or 
no  blooming  occurs;  and,  conversely,  it  is  possible  to  check 
the  growth  of  a  tree  and  bring  about  an  increased  bloom. 
It  is,  of  course,  obvious  that  vegetative  precedes  the  so- 
called  reproductive  growth,  for  the  tree  must  attain  some 
size  before  fruitage  can  be  maintained.  It  is,  nevertheless, 
convenient  to  distinguish  between  the  type  of  growth  which 
goes  to  maintain  the  tree  as  an  individual  and  effect  the 
extension  of  its  branches,  and  the  tj'^pe  which  primarily 
functions  as  the  fruit-producing  area,  thus  permitting  the 
use  somewhat  broadly  of  the  terms  vegetative  and  reproduc- 
tive tendencies. 

Jost  ^  says,  "All  factors  which  tend  to  advance  foliage 
development  are  unfavorable  to  flower  production  and 
vice  versa. "  The  experimental  evidence  in  this  country  is  not 
in  line  with  this  doctrine  but  rather  clearly  establishes  that, 
in  general,  strong  growth  is  a  natural  concomitant  of  high 
production  and  conversely  that  meagre  growth  is  associated 
with  low  yield.  Or,  as  it  has  been  expressed,  "mere  vegeta- 
tive extension  and  fruitfulness  are  not  separate  and  distinct 
functions  of  the  plant  but  each  is  an  external  expression  of 
an  internal  condition. "  ^  it  should  be  conceived  that 
increased  fruitage  may  parallel  increased  vegetation  or  it 
may  parallel  decreased  vegetation,  depending  on  the  starting 
point.  The  causes  for  this  seeming  anomaly  are  discussed 
later. 

1  Jost,  L.     Lectures  on  Plant  Physiologj\      (Eng.  Trans.)  p.  364. 
=  Kraus,  E.  J.,  and  H.  R.  Kraybill.    Ore.  Agr.  Exp.  Sta.  BuU.  149. 
1918. 


52  POMOLOGY 

48.  The  periodic  idea. — Closely  related  to  the  internal 
factors  referred  to  above  is  the  time  at  which  trees  reach  the 
bearing  age.  In  the  first  place,  as  has  been  noted,  a  given 
variety  of  fruit-tree  has  a  tendency  to  bear  at  a  definite  age: 
the  Yellow  Transparent  apple  bears  at  about  four  years  of 
age;  the  Mcintosh  at  five  or  six;  the  Baldwin  at  nine  or  ten; 
while  the  Northern  Spy  may  be  twelve  or  fifteen  years  or 
older  before  fruiting  is  established.  To  such  a  characteristic 
botanist?  have  given  the  term  "periodicity,"  although  it 
usually  refers  to  the  periodic  phenomena  of  a  single  plant. 
Jost  says,  "When  we  examine  flowering  plants  under  natural 
conditions  we  find  that  the  plant  is  'ripe  for  flowering'  just 
as  sexual  cells  appear  in  the  animal  when  it  reaches  a  certain 
age.  But  although  flower  formation,  generally  speaking, 
takes  place  at  a  certain  age,  which  diiTers  with  each  species, 
still,  exceptions  are  known,  as  for  example,  the  oak,  which 
normally  is  '  ripe '  in  its  sixtieth  year,  but  which  occasionally 
flowers  in  its  first  year  and  then  dies, "  i.  e.,  environment  may 
alter  this  particular  periodic  effect.^  While  this  does  not 
explain  the  causes  for  the  flower-bud  formation,  it  is  a 
manifestation  that  should  be  recognized. 

49.  Theory  of  specific  constructive  materials. — This 
theory,  which  has  been  proposed  by  at  least  one  plant 
physiologist  (Sachs)  and  rejected  by  some  of  the  others, 
may  be  given  brief  mention,  although  it  relates  to  plants  in 
general  and  has  no  special  reference  to  fruit-trees. 

In  attempting  to  explain  why  flower-buds  are  differentiated 
from  leaf-buds,  Sachs  suggested  that,  in  addition  to  the 
products  of  assimilation  in  the  leaf,  there  are  also  specific 
constructive  materials  which  pass  from  the  leaf  in  all  direc- 
tions and  which  collect  in  certain  quantities  where  a  definite 
organ  is  to  be  developed.  Thus,  the  flower  would  be  formed 
out  of  flower-building  material,  roots  out  of  root-building 
1  Jost,  L.    Ibid.,  p.  363. 


FRUIT-BUD  FORMATION  53 

substance,  and  so  on.  He  cites  some  interesting  experiments 
with  the  begonia.  "  In  May,  Sachs  made  cuttings  of  begonia 
in  the  usual  way,  and  found  that  the  plants  springing  from 
such  leaf  cuttings  gave  rise  to  flowers  in  the  beginning  of 
November,  preceded  by  a  luxuriant  formation  of  foliage 
leaves.  If,  however,  the  leaf  cuttings  are  taken  from  a 
flowering  specimen  in  the  end  of  July,  flowers  appear  on 
them  in  the  end  of  September,  but  few  leaves  are  previously 
formed,"  Other  cases  of  a  similar  nature  can  be  cited 
which  led  Sachs  to  announce  that  the  plant  which  was 
about  to  bloom  contained  special  flower-forming  materials 
and  hence  that  cuttings  taken  from  a  specimen  in  such 
condition  would  soon  flower,  regardless  of  the  environ- 
ment. 

Jost,^  objects  to  the  theory,  however,  and  writes,  ''This 
hypothesis  very  conveniently  explains  anomalies  and 
regeneration  phenomena,  and  this  has  won  it  a  certain 
amount  of  acceptance.  Closer  examination  shows,  however, 
that  the  difficulties  are  not  thereby  removed,  but  only 
shifted  elsewhere. " 

50.  Reserve  food. — The  accumulation  of  reserve  food 
materials  within  the  tissues  of  the  plant  has  been  commonly 
accepted  as  the  cause  of  fruit-bud  formation.  Both  bo- 
tanical and  horticultural  literature  abound  in  statements 
to  this  effect.  Sorauer  -  says,  "Plants  will  only  develop 
flowering  buds  when  the  food  material  formed  in  the  leaves 
is  copiously  stored  up  in  the  stem  and  branches  as  reserve 
material  and  not  when  this  material  is  immediately  used 
up  in  the  production  of  new  vegetative  organs  (leaves). 
Of  our  apple  trees  it  is  well  known  that  in  warm  insular  cli- 
mates they  grow  into  magnificent  foliage  trees,  but  they 

1  Adapted  from  Jost,  L.,  Ibid,  pp.  349,  364. 

2  Sorauer,  P.  A  Treatise  on  the  Physiology  of  Plants.  (Eng.  Trans.) 
p.  222. 


54  POMOLOGY 

remain  unproductive  of  fruit."  Jost  ^  states,  "It  would  ap- 
pear that  growth  is  an  essential  precedent  of  reproduction. 
It  is  so,  however,  only  in  so  far  as  growth  is  associated  with 
vigorous  assimilation,  for  it  is  shown  that  the  construction 
of  reproductive  organs  necessitates  the  previous  accumu- 
lation of  a  certain  amount  of  nutritive  materials,  and  these 
must  be  all  the  more  abundant  the  more  complex  the  re- 
productive organs  are." 

Fruit-growers,  especially,  have  assumed  that  there  is  abun- 
dant evidence  indicating  that  overbearing  of  trees  results 
in  exhaustion  of  their  "reserves"  and,  consequently,  in  alter- 
nate or  irregular  bearing  also,  if  indeed  the  trees  are  not 
permanently  incapacitated.  It  must  also  be  recognized 
that  exhaustion  may  be  concerned  with  very  different  clas- 
ses of  reserves  and  this  makes  it  evident  that  the  remedies 
for  unfruitfulness  may  vaiy  greatly  in  practice.  In  general, 
however,  the  formation  of  fruit-buds  in  abundance  on  the 
young  trees  is  preceded  by  a  decrease  of  growth  extension 
and  the  accumulation  of  reserve  food  materials,  and  further- 
more by  a  proper  balance  of  them  within  the  tissues  of  the 
plant.  Of  the  reserve  materials  that  have  been  considered 
to  play  a  large  part  in  the  process  are  carbohydrates,  nitro- 
gen- and  phosphorus-complexes,  and  fats, 

51.  Carbohydrates,  nitrogen-complexes,  and  moisture. — 
It  is,  of  course,  understood  that  carl^ohydrates  are  products 
of  assimilation  by  green  plants  and  that  they  constitute  one 
of  the  largest  groups  of  organic  compounds  that  are  stored 
as  reserve  foods.  Of  the  carbohydrates, — starch,  sucrose, 
dextrose  and  levulose, — starch  is  by  far  the  most  abundant 
form  in  which  they  are  deposited  as  a  reserve,  although  cane- 
sugar  or  sucrose  is  found  in  considerable  amounts,  depend- 
ing on  the  plant.  It  is  probable  also  that  hemicelluloses 
and  pentosans  constitute  an  important  part  of  the  reserves 
1  Jost,  L.,  Ibid.  p.  357. 


FRUIT-BUD  FORMATION  55 

of  the  fruit-tree.  Fats  are  present  as  reserves,  but  in  smaller 
quantities  than  the  other  two  and  are  not  considered  further 
in  this  connection. 

Nitrogen  is  essential  in  the  protein  sjaithesis  in  plants, 
and  is  a  necessaiy  component  of  all  protoplasmic  materials. 
This  element  is  frequently  calculated  as  total  nitrogen  in 
analyses  of  plant  tissues,  no  effort  being  made  to  separate 
the  various  complexes,  or  it  may  be  determined  in  any  of  its 
various  combinations.  Practically  all  of  this  element  is 
derived  from  the  soil  as  nitrates.  Whether  these  are  decom- 
posed and  made  available  for  protein  synthesis  in  the  leaves 
alone  or  in  other  tissues  appears  not  to  be  entirely  clear  at 
the  present  time.  It  has  been  widely  accepted  that  the 
nitrates  reach  the  leaves  through  the  water-conducting 
tissues  (xylem  of  woody  plants),  but  recently  it  has  been 
argued  that  a  major  portion  is  transported  through  the 
cortical  layer  (phloem).^  The  relation  of  the  nitrogen  in  its 
various  forms  to  the  available  carbohydrate  and  water  sup- 
ply seems  to  be  of  special  significance  in  connection  with 
the  differentiation  of  flower  primordia. 

Moisture  likewise  is  essential  in  the  process  of  flower-bud 
formation,  as  it  is  in  all  other  phases  of  gro^vth.  It  is  neces- 
sary for  digestion,  conduction,  transpiration,  photosyn- 
thesis, and  various  other  synthetic  processes. 

These  products  and  materials  are  found  in  the  branches, 
trunk,  and  roots  of  the  tree  in  somewhat  vaiying  amounts 
at  different  times  of  the  year.  They  are  constantly  under- 
going change,  even  during  much  of  the  dormant  season. 
The  cany-over  effects  of  these  materials  from  one  season 
or  year  to  another  are  of  the  very  greatest  importance  in 
coraiection  with  the  early  growth  in  spring,  blooming,  and 
indeed  the  initiation  of  fruit-bud  development.  They  are 
quite  as  important  as  the  materials  present  in  the  soil  about 
1  Curtis,  Otis  F.    Amer.  Jour.  Bot.  7:  101-124.    March,  1920. 


56 


POMOLOGY 


the  tree,  for  it  must  be  remembered  that  the  type  of  early 
activity  manifested  by  the  growing  tree  is  controlled  quite 
as  much  by  the  character  of  its  reserves  as  by  the  materials 
which  it  absorbs  from  the  media  surrounding  it.  It  is  the 
joint  interaction  or  balance  of  the  two  which  determines 
the  character  of  growth. 

52.  Relation  of  these  materials  to  flowering  of  plants. — 
(See  Fig.  22.)    A  favorite  theme  of  speculation  by  botanists, 


Class   4 

Fig.  22. — Diagram  to  illustrate  the  hypotheses  involved  in  Classes  I, 
II,  III,  and  IV.  To  right  of  dotted  line:  fruitfulness  will  increase 
for  a  time  as  vegetation  decreases  from  the  maximum,  but  will  then 
decrease  as  vegetation  approaches  the  minimum.  Going  in  the 
other  direction,  as  vegetation  increases  from  the  minimum  fruit- 
fulness  will  increase  for  a  time,  but  vegetation  will  persist  beyond 
fruitfulness  in  either  direction.  To  the  left  of  the  dotted  line 
vegetation  may  either  decrease  from  the  maximum  or  increase 
from  the  minimum  without  affecting  fruitfulness  provided  the 
plants  are  in  the  condition  described  in  either  Class  I  or  II. 

horticulturists,  and  others  interested  in  vital  phenomena, 
has  been  the  causes  that  underlie  the  flowering  and  fruiting  of 
plants.  Horticulturists  have  usually  approached  the  problem 
by  means  of  the  field-trial  route.  Practically  the  whole  cate- 
gory of  cultural  practices  has  been  brought  into  play  in 
attempting  to  regulate  fruitfulness.     But  of  special  promi- 


FRUIT-BUD  FORMATION  57 

nence  has  been  the  appUcation  of  the  various  "essential" 
elements  of  plant  nutrients,  either  by  means  of  cultivation, 
green-manuring,  or  animal  or  artificial  manures.  These 
various  treatments  have  not  ])een  without  their  results  from 
an  economic  standpoint,  but  the  field  still  remains  open  to 
investigators  interested  in  determining  the  part  played  by 
these  elements  and  their  inter-relation. 

The  investigations  and  interpretations  of  Kraus  and  Kray- 
bill  are  highly  significant  and  are  of  interest  in  this  comiection. 
The  statements  or  premises  which  they  have  postulated 
are  given  here  verbatmi.  The  abbreviations  follow- 
ing the  various  items  are:  M  =  moisture;  N=  nitrogen- 
complexes  (especially  nitrates) ;  C  =  carbohydrates.  These 
formulae  are  not  a  part  of  the  original  article  and  they  are 
not  to  be  taken  as  actual  ratio  expressions, 

I.  Though  there  be  present  an  abundance  of  moisture 
and  mineral  nutrients,  including  nitrates,  yet  without  an 
available  carbohydrate  supply,  vegetation  is  weakened  and 
the  plants  are  non-fruitful;  M/N — C=  non-fruitful. 

II.  An  abundance  of  moisture  and  mineral  nutrients, 
especially  nitrates  coupled  with  an  available  carbohydrate 
supply,  makes  for  increased  vegetation,  barrenness,  and 
sterility;  M/N+C=  non-fruitful. 

III.  A  relative  decrease  of  nitrates  in  proportion  to  the 
carbohydrates  makes  for  an  accumulation  of  the  latter,  and 
also  for  fruitfulness,  fertility,  and  lessened  vegetation;  N/C 
— N  =  fruitful. 

IV.  A  further  reduction  of  nitrates  without  inhibiting 
a  possible  increase  of  carbohydrates,  makes  for  a  suppres- 
sion both  of  vegetation  and  fruitfulness.    C — N  =  non-fruitful , 

According  to  these  views,  the  behavior  or  response  of  the 
trees  as  regards  growth  and  fruitfulness  is  not  entirely  a 
matter  of  total  amount  of  nutrient  or  food  materials  avail- 
able, but  a  proper  balance  or  relation  between  them  as  well. 


58  POMOLOGY 

It  also  means  that  it  is  essential  to  study  the  ways  in  which 
various  cultural  practices  affect  these  materials.  That 
abundant  storage  of  carbohydrates  is  associated  with  non- 
fruitfulness  as  truly  as  under-storage,  is  here  brought  out 
in  contradistinction  to  the  opinions  of  some  other  workers. 
An  interesting  example  of  lack  of  balance  of  these  materials 
and  the  results  obtained  when  such  balance  is  restored  is 
noted  in  the  case  of  an  experimental  orchard  in  Oregon.^ 
The  apphcation  of  quickly  available  nitrogenous  fertilizers 
gave  almost  immediate  and  conspicuous  results  in  an  or- 
chard which  was  unfruitful  and  making  very  little  growth 
extension.  The  suggested  interpretation  of  these  results 
was  to  the  effect  that  there  was  probably  a  condition  of 
large  amount  of  carbohydrates  in  the  trees  and  a  low  supply 
of  nitrate  in  the  soil,  and  when  this  latter  was  increased  the 
carbohydrates  could  be  utilized  in  the  production  and  devel- 
opment of  fruit.  This  is  an  interesting  explanation  of  a 
very  common  experience  in  orchard  fertilizer  experiments. 
The  theory,  that  the  addition  of  sufficient  nitrates  and  mois- 
ture to  balance  an  accumulation  of  starch  and  other  stor- 
age materials  within  the  tissues  of  the  plant,  serves  as  a  nec- 
essary accompaniment  of  growth  and  bud  formation,  can 
find  ready  acceptance  with  those  who  have  seen  such  or- 
chard experiments.  Fruitf  ulness  would  be  decreased  if  plants 
were  reduced  from  III  to  II  but  in  the  case  cited  they  were 
shifted  from  IV  to  III  with  consequent  fruitfulness. 

It  has  been  suggested  also  that  top-  as  well  as  root-prun- 
ing of  trees  upsets  the  balance  of  the  carbohydrate-nitro- 
gen-moisture combination,  which  appears  to  influence  so 
markedly  the  formation  of  fruit-buds.  The  reserve  mate- 
rials of  the  tree  are  reduced  by  top-pruning  (see  discussion 
in  Chapter  V),  resulting  in  their  limitation  relative  to  the 

^  Lewis,  C.  I.,  and  G.  G.  Brown.  Rept.  Hood  River  Branch  Exp.  Sta. 
(Ore.).     1916. 


FRUIT-BUD  FORMATION  59 

soil  solutes  which,  according  to  the  generalization  above, 
would  depress  flower  formation.  Or  if  the  roots  are  pruned, 
it  would  result  in  a  preponderance  of  "reserves"  over  soil 
solutes  taken  up  by  the  roots,  producing  again  a  lack  of 
balance  but  in  the  ojiposite  direction. 

53.  Relation  of  leaf  area  to  flowering. — The  relation  of 
the  amount  of  leaf  surface  and  the  size  of  the  leaves  to  fruit- 
bud  formation  is  germane  to  this  discussion,  as  it  is  connected 
with  the  food  supply  which  can  be  utilized  by  the  plant. 
It  should  not  be  inferred  that  large  leaves  are  necessarily 
associated  with  the  formation  of  fruit-buds,  for  frequently 
the  largest  leaves  appear  on  the  strongest  vegetative  shoots 
which  are  usually  barren  (?.  c,  water-sprouts).  However, 
it  has  been  observed  that  the  year  an  apple  tree  is  fruiting 
heavily,  the  leaves  are  usually  smaller  than  when  little  or 
no  fruit  is  bome.  This  refers  particularly  to  the  leaves  on 
the  spurs.  A  report  on  two  Yellow  Transparent  apple  trees 
which  had  manifested  a  noticeable  difference  in  leaf  size 
between  the  bearing  and  non-bearing  years  may  be  cited  as 
illustrative  of  this  point.  It  will  be  understood  that  the 
bearing  tree  one  year  is  non-bearing  the  next: 

Table  VIII 

AVER.\r.E  WEIGHT  AND   AREA  A  LEAF;  BEARING  AND  NON-BEARING  TREES 


Sample 

Air  dry 

weight  in 

grams 

Area 

in 
sq.  in. 

Average 
difference  in 
area  sq.  in. 

Bearing  trees 

1913 
"1914 

.2.5.35 
.2010 

4.7320 
5.1633 

Non-bearing  trees . 

1913 
"1914 

.4226 
.3150 

7.0.584 
6.9972 

2.0802 

It  has  also  been  observed  that  there  are  more  as  well  as 
larger  leaves  on  the  cluster  base  or  on  the  spur  the  season 


60  POMOLOGY 

that  fruit-buds  are  formed  (in  the  case  of  biennial  bearers), 
and  it  may  also  be  inferred  that  the  total  leaf  area  of  the  tree 
is  greater  in  the  non-bearing  year. 

54.  Effect  of  leaves  on  parts  immediately  surrounding 
them. — Carefully  conducted  experiments  under  widely 
different  climatic  conditions  have  established  the  fact  that 
formation  of  fruit-buds  depends  to  a  large  extent  on  the 
leaves  innnediately  adjacent  to  them.  However,  a  state- 
ment does  not  explain  this  fact  nor  does  it  imply  that  all 
buds  adjacent  to  leaves  are  developed  into  fruit-buds.  In 
the  case  of  apples,  for  example,  the  larger  number  of  axillary 
buds  are  leaf-buds,  and  with  the  stone-fruits  many  such 
buds  give  rise  to  a  leafy  shoot.  The  work  of  Magness,^ 
however,  has  shown  that  buds  are  not  likely  to  become  dif- 
ferentiated into  fruit-buds  unless  the  leaves  immediately 
adjacent  to  or  subtending  them  are  intact.  Varieties  of 
plum  and  apple  that  are  likely  to  fonn  axillary  fruit-buds 
were  treated  by  defoliating  the  alternate  leaves  along 
the  current  season's  shoot.  As  a  result,  fruit-buds  were 
formed  only  at  the  nodes  where  the  leaves  were  not 
removed. 

In  the  case  of  defoliated  spurs,  the  results  were  more  va- 
riable, but  the  tendency  was  much  the  same  as  in  the  case 
of  the  new  shoots. 

In  line  with  these  observations,  the  work  of  Jones-  is  sig- 
nificant. He  calls  attention  to  the  large  storage  of  reserve 
materials  in  the  maple  tree.  Since  all  the  carbohydrates 
are  manufactured  in  the  green  leaves  under  the  influence 
of  sunlight,  the  sugar-content  of  the  sap  depends  on  the 
conditions  of  the  preceding  season  as  to  sunlight  and  leaf 
development.    He  has  stated  that  in  recent  years  there  has 

1  Magness,  J.  R.  Ore.  Agr.  Exp.  Sta.  Bull.  146.  Harvey,  E.  M.,  and 
A.  E.  Murneek.    Ore.  Agr.  Exp.  Sta.  Bull.  176.    1921. 

2  Jones,  C.  H.,  et  al.    Vt.  Agr.  Exp.  Sta.  Bull.  103. 


FRUIT-BUD  FORMATION  61 

been  abundant  evidence  of  this  fact,  for  when  the  trees  are 
defoliated  by  caterpillars,  the  following  season  the  sap  car- 
ried much  less  sugar  than  usual.  He  also  writes  that,  as  the 
leaf  area  varied  from  year  to  year,  so  the  capacity  to  form 
carbohydrates  varied  in  proportion.  It  was  further  observed 
that  a  tree  standing  in  the  open  with  well-developed 
branches  and  large  leaves  produced  more  and  richer  sap 
(4.39  per  cent  sugar)  than  those  growing  in  dense  brush 
with  small  leaves  (2.14  per  cent  sugar). 

55.  Horticultural  practices  that  influence  fruit-bud 
formation. — ^After  it  is  recognized  that  the  immediate 
cause  of  fruit-bud  dilTerentiation  is  within  the  tree  itself, 
the  evidence  of  external  factors  related  to  such  cause  may 
be  considered.  As  in  the  case  of  the  internal  factors,  it  is 
not  possible  to  consider  the  external  ones  entirely  individu- 
ally, for  they  are  closely  inter-related.  Several  may  bring 
about  a  clear-cut  response  by  the  tree,  either  an  abun- 
dant formation  of  fruit-buds  or  excessive  vegetative  growth 
and  barrenness. 

Among  the  practices  that  may  affect  the  tree  in  such  a 
way  as  to  bring  about  fruit-bud  formation  may  be  listed  the 
following:  cultural  methods  (using  the  tenn  in  a  broad  sense) ; 
top-  and  root-pruning;  ringing;  grafting  on  slow-growing 
stock  (dwarfing);  fertilizing  and  methods  for  controlling 
insect  and  disease  pests,  thus  protecting  the  foliage.  Some 
are  special  or  extreme  measures  and  are  not  ordinarily  to 
be  recommended,  while  others  are  regular  orchard  opera- 
tions. 

56.  Cultural  practices. — In  Chapter  VIII  it  is  shown 
that  favorable  soil  conditions  must  be  provided  if  maximum 
commercial  results  are  to  be  secured.  Neither  over-  nor  under- 
vegetative  trees  are  fruitful  and  obviously  require  dissimilar 
treatment.  In  the  case  of  trees  which  are  growing  too  vig- 
orously, it  is  probable  that  an  abundant  supply  of  nitrates 


62  POMOLOGY 

is  available  together  with  ample  water,  and  in  order  to  cor- 
rect the  over-vegetative  condition  any  of  several  cultural 
practices  may  be  discontinued.  The  simplest  plan  might 
be  to  seed  the  orchard  down  to  grass  if  it  is  being  tilled ;  or 
to  discontinue  the  use  of  fertilizers  and  manures;  to  reduce 
the  number  of  cultivations;  to  discontinue  the  use  of  cover- 
crops;  or  in  some  other  way  to  reduce  the  nitrates  and  mois- 
ture available  to  the  trees  until  a  better  ''balance"  is  main- 
tained. 

Under-vegetative  and  unfruitful  trees,  on  the  other  hand, 
require  opposite  treatment.  The  probability  is  that  there 
is  a  lack  of  nitrates  and  perhaps  moisture  in  such  cases,  a 
condition  which  has  already  been  referred  to  (p.  58).  This 
situation  is  representative  of  more  unfruitful  orchards 
than  the  over-vegetative  ones  cited  above.  Here  also  sev- 
eral treatments  may  be  applied:  fertilization  with  some 
quickly  available  nitrogenous  materials;  tillage;  the  use  of 
leguminous  cover-crops;  perhaps  the  ranging  of  poultry  in 
the  orchard;  or  in  some  other  way  to  improve  the'  mois- 
ture conditions  of  the  soil  and  to  supply  nitrates  to  the 
trees. 

Again  reverting  to  the  proposal  of  Kraus  and  Kraybill, 
the  following  outline  may  be  suggestive  of  means  of  regu- 
lating the  growth  behavior  of  trees.  It  illustrates  an  im- 
portant point  of  their  work,  namely,  that  there  is  often  a 
double  and  apparently  opposite  effect  of  some  orchard  prac- 
tices. In  other  words,  it  is  not  the  method  in  itself  which  is 
most  important  but  rather  the  relationship  of  materials  it 
influences  under  varying  circumstances,  as  indicated  in  the 
following  outline: 


FRUIT-BUD  FORMATION 


Relatively  increasing  carbohydrates 


Relatively  increasing  nitrogen 


I 
Nitrogen+(not 

limiting) 
Carbohydrates — 

(limiting). 


II 

Xitrogen  +  (not 
limiting  to  use 
of  carbohydrates 
in  vegetation) 

Carbohydrates+ 
(not  limiting). 


Ill 

Nitrogen  +  (lim- 
iting use  of  car- 
bohydrates in 
vegetation) 

Carbohydrates+ 
(not  limiting). 


(lim- 


IV 
Nitrogen  — 

iting) 
Carbohydrates -H 

(not  limiting). 


Light  pruning  of 
natural  growth 
tendencies. 
N.  decreasing 
through  utiliza- 
tion by  tree  if 
not  renewed,    y 


Lighter  pruning, 
less  N.  fertilizer. 


Excessive  prun- 
ing, shading  of 
trees. 


Heavy    pruning, 

heavy    N.    ferti- 
lizer, 
heavy  moisture.  , 


No  pruning,  dry 
soil,  no  fertilizer. 


Pruning,  N.,  fav 
tilization,  cul- 
tivation, etc. 


57.  Pruning. — The  relation  of  pruning  to  fruit-bud  for- 
mation has  ah-eady  been  illustrated  in  part  by  the  above 
outline  and  the  subject  is  treated  more  fully  in  Chapter  V. 
Since  root-pruning  is  less  frequently  practiced  than  top- 
pruning,  it  is  l)riefly  discussed  in  this  connection.  Summer 
pruning  is  taken  up  later  (p.  98),  but  it  is  sufficient  to  say  at 
this  pomt  that  summer  pinching,  particularly  on  the  peach, 
results  in  the  formation  of  an  increased  number  of  fruit- 
buds  on  short  spurs.  More  extensive  summer  pruning  has 
not  proved  desirable  in  eastern  United  States,  but  certain 
types  find  some  limited  use  under  western  conditions. 

Root-pruning  has  long  been  advocated  as  a  means  of 
causing  barren  trees  to  bear  fruit.  The  theory  was  that,  by 
cutting  off  a  portion  of  the  roots,  the  intake  of  water  (and 
unelaborated  food  materials)  and  hence  the  sap  flow  was 
reduced,  and  this  brought  about  a  relative  preponderance 


64  POMOLOGY 

of  reserve  materials.  Drinkard's  ^  experiments  with  root- 
pruning,  however,  show  this  practice  to  be  of  questionable 
value,  if  not  injurious.  The  work  was  conducted  with  dwarf 
trees  and  may  have  been  unusually  severe.  While  fruit-bud 
formation  was  stimulated  to  a  marked  degree  when  the 
trees  were  severely  root-pruned,  the  effect  on  the  trees  was 
so  devitalizing  that  the  fruit  which  set  and  matured  was 
small  in  quantity  and  size,  and  hence  the  advantages  were 
more  than  outweighed  by  the  serious  results  of  the  treat- 
ment. When  spring  pruning  was  also  practiced  with  the 
root-pruned  trees,  the  stimulus  to  fruit-bud  formation  was 
generally  less  pronounced  and  the  trees  suffered  seriously 
as  in  the  case  above  noted. 

58.  Ringing. — By  the  ringing  of  fruit-trees  is  meant  the 
operation  of  removing  a  ring  of  bark  from  the  trunk  or 
branches.  This  is  an  ancient  European  practice  which  has 
not  only  been  used  to  increase  fruitfulness  but  also  to  im- 
prove the  size  of  fruit,  as  with  the  grape.  The  ring  may 
vary  in  width  but  it  is  usually  not  over  an  inch  or  two, 
and  a  half  inch  will  accomplish  the  desired  results  as  readily. 
The  ring  may  be  removed  at  any  point,  usually  in  late  spring 
or  early  summer,  preferably  a  little  earlier  than  the  time 
the  fruit-buds  are  beginning  to  differentiate.  In  peeling 
off  the  bark,  the  tissues  to  the  cambium  are  removed  and, 
if  this  underlying  tissue  is  uninjured  and  does  not  dry  out,  it 
will  immediately  begin  to  form  new  cells  and  a  cortical  layer 
will  be  laid  down  shortly.  If  the  ringing  is  done  before 
active  growth  starts  in  the  spring,  the  chances  of  new  tissue 
forming  are  much  reduced  and  bridge-grafting  may  have 
to  be  resorted  to  if  the  tree  is  to  be  saved,  for  the  callus  which 
is  thrown  out  at  the  wound  will  rarely  be  sufficient  entirely 
to  heal  the  wound. 

Results  similar  to  those  obtained  by  artificial  ringing  are 

1  Ann.  Kept.  Va.  Poly.  Inst.  1913  and  1914. 


FRUIT-BUD  FORMATION  65 

often  observed  when  a  tree  is  suddenly  injured  by  freezing, 
fire,  disease  (canker),  mice,  or  similar  agency. 

The  supposition  in  all  these  cases  has  been  that  there  was 
an  accumulation  of  reserves  throughout  the  tissues  above 
the  wound  and  this  was  favorable  to  the  differentiation  of 
flowering  parts.  Since  experiments  have  recently  indicated 
that  a  major  part  of  the  nitrates  may  be  transported  up 
through  the  cortical  .tissues  as  well  as  that  carbohydrates 
are  carried  down  through  them,  it  would  seem  that  a  sudden 
transfer  from  Class  I  or  II  to  that  of  Class  III  may  take  place, 
owing  to  the  interruption  in  the  supply  of  available  nitrates, 
and  consequent  accumulation  of  carbohydrates.  Usually 
the  leaves  of  ringed  trees  soon  turn  yellowish  and  are  checked 
in  their  growth,  which  indicates  a  lack  of  nitrogen.  If 
this  is  true,  then  an  important  factor  is  introduced  in  connec- 
tion with  any  accumulation  of  reserves  which  may  take 
place,  to  bring  about  a  condition  for  flowering. 

Drinkard's  results  in  ringing  dwarf  trees  indicate  that, 
for  the  conditions  with  which  he  worked,  the  greatest  flower- 
ing was  secured  when  the  ringing  was  done  on  May  31st, 
to  a  less  degree  on  June  23d,  and  no  results  were  obtained 
when  it  was  performed  April  23d.  On  the  other  hand,  the 
author  obtained  a  100  per  cent  bloom  when  mature  trees 
were  ringed  on  April  30  (in  New  Hampshire),  as  compared 
with  a  35  per  cent  bloom  on  adjacent  untreated  trees.  The 
trees  were  seriously  impaired,  however,  as  a  result  and  bridge- 
grafting  was  resorted  to.  This  difference  was  obviously 
due  either  to  a  dissimilar  condition  of  the  reserves  in  the  tops 
of  the  trees  or  to  an  unlike  soil  condition,  as  well  as  to  the 
age  and  variety  of  the  trees. 

Howe  1  ringed  a  block  of  five-year-old  trees  in  New  York 
State  with  marked  results  in  flowering,  but  the  general 
effect  on  the  trees  was  devitalizing  and  it  was  concluded  that 

1  N.  Y.  [Geneva]  Agr.  Exp.  Sta.  Bull.  391.    1914. 


66  POMOLOGY 

such  a  practice  was  not  to  be  recommended.  The  work  was 
repeated  the  following  season  with  twenty-seven  of  the 
trees,  but  the  second  ringing  did  not  result  in  again  stimu- 
lating fruit-bud  formation,  for  while  these  particular  trees 
averaged  93  per  cent  of  a  crop  to  a  tree  in  1911,  they  yielded 
only  43  per  cent  in  1912.  Again  the  following  year  these 
same  trees  were  ringed  in  June.  This  thne  rings  of  3,  6,  9, 
12,  15,  18,  and  21  inches  in  width  were  made,  four  trees  being 
used  for  each  of  the  various  widths.  These  wounds  were 
made  around  the  trunks  just  above  the  former  rings,  all  of 
the  bark,  whether  in  three-inch  or  twenty-one-inch  strips, 
being  removed  with  equal  ease.  This  ringing  had  no  effect 
on  stimulating  fruit-bud  production,  for  the  crop  borne  in 
1913  was  about  the  same  as  that  of  1912.  Injurious  effects 
were  experienced  in  the  vigor  of  the  trees,  however,  and 
the  wider  the  bands  the  more  serious  the  injury. 

The  practice  of  ringing  cannot  be  applied  to  stone-fruits 
as  they  are  practically  always  killed  as  a  result  of  the  oper- 
ation, no  new  tissue  being  formed  over  the  decorticated  area. 

In  the  work  of  Alderman  and  Auchter  ^  with  seven-year- 
old  standard  trees,  the  usual  results  were  secured  but  the 
succeeding  year  the  treated  trees  produced  little  or  no  fruit. 
They  state  at  the  conclusion  of  the  experiment  that:  ''From 
the  results  of  our  observations,  ringing  plainly  checks  the 
vigor  of  the  tree  for  at  least  three  years  and  although  it  has 
been  successful  in  causing  trees  to  bear  the  year  following  the 
operation,  this  bearing  has  not  been  established  as  a  habit." 

Hence  from  the  work  here  considered  and  from  that  of 
others  ^  it  is  seen  that  ringing  apple  trees  at  the  proper  time 

1  W.  Va.  Agr.  Exp.  Sta.  Bull.  158. 

2Sorauer,  P.  Physiology  of  Plants.  (Eng.  Trans.)  pp.  159-164. 
Paddock,  W.  N.  Y.  Agr.  Exp.  Sta.  Bull.  151.  Daniel,  L.  Compt. 
Rend.  Acad.  Sci.  (Paris)  i,'^/;1253-1255.  1900.  Sablon,  Leclerc  du. 
Compt.  Rend.  Acad.  Sci.  (Paris)  / 40. -1553- 1555.    1905. 


FRUIT-BUD  FORMATION  67 

will  increase  fruit-bud  formation  but  is  a  drastic  measure 
and  should  only  be  resorted  to  in  extreme  cases.  With  the 
grape  the  situation  is  somewhat  different.  Husmann  ^ 
has  shown  that  with  the  currant  grape,  ringing  is  not  only- 
practical  but  entirely  necessary.  The  ringing  with  this  fruit 
must  be  done  annually  and  when  the  vines  are  in  bloom. 
Ringing  improved  the  size,  quality,  and  quantity  of  the 
fruit. 

59.  Stripping.^What  may  be  considered  a  modified 
form  of  linging  was  used  by  Drinkard  in  his  experiments. 
This  consisted  in  the  removal  of  strips  of  bark,  one-fourth 
to  one-half  inch  iii  width,  from  the  trunk  of  the  tree,  beginning 
near  the  surface  of  the  ground  and  extending  up  to  and 
frequently  above  the  main  branches.  Several  of  the  main 
branches  were  stripped  for  a  distance  of  twelve  or  eighteen 
inches.    Three  to  five  such  strips  were  taken  from  each  tree. 

When  this  stripping  was  applied  to  trees  which  had  been 
pruned  in  the  spring,  the  treatment  gave  no  stimulation  to 
fruit-bud  formation,  but  in  the  absence  of  the  pruning 
fruit-bud  formation  was  stimulated  markedly  and  a  good 
crop  of  fruit  was  obtained.  The  trees  did  not  suffer  from  the 
process  of  stripping  but  remained  green  and  vigorous  through- 
out the  season. 

60.  Bending. — In  the  older  horticultural  literature  fre- 
quent mention  is  made  of  the  advantage  to  be  gained  by 
bending  the  shoots  or  branches  in  order  to  cause  fruit-bud 
formation.  This  doctrine  seems  to  have  been  accepted  and 
based  on  the  principle  that  "The  more  the  sap  is  obstructed 
in  its  circulation,  the  more  likely  it  will  be  to  produce  fruit- 
buds."  On  the  contrary,  it  was  stated  that  if  a  fruit  branch 
is  to  be  changed  into  a  wood  branch,  it  should  be  given  a 
vertical  position. 

1  Husmann,  George  C.  Developing  new  grape  industries.  Proc. 
Amer.  Soc.  Hort.  Sci.     1918. 


68  POMOLOGY 

Gardner  '  has  conducted  an  experiment  on  the  bending 
of  dormant  shoots  into  vertical,  horizontal,  or  downward 
positions,  and  reports  that  no  advantage  is  to  be  gained  by 
the  practice,  "Its  most  important  influence  is  to  reverse 
the  relative  locations  of  spurs  and  branch  shoots  on  any 
single  season's  wood  that  is  bent  and  such  a  reversal  cannot 
be  regarded  as  worth  the  cost  if  indeed  it  is  in  any  way 
desirable." 

61.  Dwarfing  of  fruit-trees,  which  is  accomplished  by 
working  them  on  slow-growing  stock,  is  commonly  advocated 
as  a  means  of  bringing  them  into  earlier  bearing.  Doubtless 
considerable  misapprehension  exists  on  this  matter.  Although 
some  precocity  in  bearing  is  often  obtained,  veiy  little  is 
gained  in  the  yield  of  commercial  crops.  Hedrick  -  conducted 
the  most  extensive  experiment  with  dwarf  apples  that  has 
been  reported  in  this  country,  but  several  unavoidable 
inequalities  crept  into  the  work  during  its  progress  so  that 
the  results  were  affected  in  some  particulars.  Trees  were 
worked  on  Crab  (standard),  Doucin  (half  dwarf),  and 
Paradise  (full  dwarf)  stocks.  The  differences  in  yield  at  the 
time  the  results  were  reported  (after  ten  years)  were  not 
great,  but  there  seemed  to  be  little  preference  between  the 
French  Crab  and  the  Doucin  stocks  while  the  full  dwarfs 
had  produced  lower  yields.  The  general  conclusions  of  the 
author  were  to  the  effect  that  dwarf  fruit-trees  have  no  place 
in  a  commercial  orchard. 

62.  Thinning  is  commonly  cited  as  a  means  of  bringing 
about  annual  bearing.  While  additional  data  may  modify 
the  present  view,  it  can  be  stated  briefly  that  such  an  in- 
fluence on  fruit-bud  formation  has  not  been  accomplished 
with  mature  apple  trees  but  has  been  reported  experimentally 
with  the  peach  and  apricot.     With  these  fruits  it  has  not 

1  Gardner,  V.  R.    Ore.  Agr.  Exp.  Sta.  Bull.  146. 

2  N.  Y.  (Geneva)  Agr.  Exp.  Sta.  Bull.  406. 


FRUIT-BUD  FORMATION  69 

only  influenced  the  succeeding  crop  but  also  the  crops  for 
several  seasons  afterward. 

63.  Individuality. — Aside  from  the  many  and  varied 
factors  that  influence  fruit-bud  formation,  the  trees  them- 
selves are  to  be  considered.  Some  trees  in  an  orchard  may 
be  consistently  high  yielders,  and  others  veiy  low.  But 
whether  this  is  due  to  an  hereditaiy  difference  which  can  be 
perpetuated  is  an  open  question,  with  the  burden  of  proof 
on  those  who  claim  such  to  be  the  case.  Whether  it  is  due 
to  a  difference  in  the  original  bud  or  cion  or  in  the  rootstock 
is  not  clear  at  present.  Probably  it  is  most  frequently 
traceable  to  environmental  factors  which  may  not  be  ap- 
parent. 

64.  Climate  is  the  sum  of  all  the  weather  conditions 
and  has  a  definite  effect  on  the  growth  behavior  of  the  trees. 
If  northern  fruits  such  as  the  apple  are  grown  in  the  tropics, 
the  growth  is  one  of  vegetative  extension  only.  In  the 
temperate  zone  a  balance  between  vegetative  and  reproduc- 
tive growth  is  manifest,  while  still  further  north  there  is  a 
tendency  to  somewhat  dwarfer  trees  and  increased  fruitful- 
ness.  If  it  is  accepted  that  there  are  different  optima  of 
temperature  for  the  maximum  development  of  the  several 
plant  parts,  then  it  may  be  assumed  that  some  varieties  of 
fruit  will  develop  flowering  parts  more  readily  under  one 
climatic  condition  than  another,  other  things  being  equal. 
Therefore,  climate,  as  is  discussed  later,  plays  its  part  in  the 
flowering  and  fruiting  of  trees. 

65.  Plants  threatened  by  death. — The  statement  is 
commonly  made  that  if  a  tree  is  seriously  injured  or  threat- 
ened by  death,  it  will  make  a  last  effort  to  reproduce  itself 
before  it  dies.  The  reason  assigned  for  the  phenomenon 
seems  sentimental  and  offers  no  real  interpretation.  That 
such  a  tree  does  flower  freely  is  sometimes  true  but  more 
frequently  it  is  not.    When  it  occurs,  frequently  a  condition 


70  POMOLOGY 

similar  to  "ringing"  takes  place  with  its  attendant  results  as 
discussed  previously;  i.  e.,  disease  such  as  canker,  or  forms 
of  winter-injuiy,  damage  by  rodents  or  borers,  or  mechanical 
injuries,  may  interfere  with  the  flow  of  the  sap  through  the 
tissues  of  the  tree.  Just  what  disturbance  occurs  in  the 
reserves  of  the  tree  might  have  to  be  determined  for  any 
given  case,  but  it  would  be  explained  on  the  basis  of  nutrition 
entirely. 

66.  Light. — That  a  close  relationship  obtains  between 
the  amount  of  light  available  and  the  production  of  fruit- 
buds  must  be  patent  after  a  consideration  of  the  foregoing 
paragraphs.  Throughout  this  discussion  it  has  been  pointed 
out  from  various  angles  that  the  amount  of  elaborated  food 
materials  within  the  plant  together  with  their  quantitative 
relation  (and  probably  a  qualitative)  to  one  another  consti- 
tutes the  crux  of  the  entire  problem.  Since  the  synthesis  of 
many  of  the  plant  products  is  dependent  on  light  as  a  source 
of  energy,  it  is  apparent  that  neither  vegetative  extension 
nor  the  differentiation  of  flowering  parts  could  proceed 
without  a  proper  amount  of  light.  Just  what  intensity  and 
duration  of  light  is  necessaiy  for  the  maximum  production  of 
flower  parts  is  not  now  known.  In  general,  it  requires  a 
greater  light  intensity  for  flower-bud  formation  than  for 
vegetative  development.  This  is  seen  in  the  comparative 
lack  of  flowering  in  the  interior  of  dense  unpruned  trees. 
Not  only  is  fruit-bud  formation  partially  suppressed  under 
these  conditions,  but  the  growth  is  weakly  vegetative  and 
if  the  shading  continues  the  spurs  and  branches  die. 

In  Plate  I  is  shown  the  effect  of  shading  a  peach  tree  with 
a  light-weight  cotton  cloth.  The  twig  to  the  left  was  taken 
from  an  adjacent  unshaded  tree  of  the  same  variety.  It 
will  be  noted  that  there  is  a  suppression  of  branching  in  the 
shaded  tree  and  usually  only  one  leaf  occurs  at  a  node.  This 
modification  in  growth  necessarily  lessens  the  number  of 


FRUIT-BUD  FORMATION  71 

fruit-buds  which  can  be  formed  because  of  the  reduction  in 
fruiting  area,  but  even  on  the  shoots  which  were  produced 
there  was  a  preponderance  of  leaf-buds,  apparently  due  to 
shading.  The  knowledge  on  this  subject  is  meager,  however, 
and  there  is  need  for  additional  research. 

It  has  recently  been  pointed  out  that  the  length  of  exposure 
to  sunlight  is  of  the  greatest  importance  in  the  growth  and 
development  of  plants,  particularly  with  respect  to  sexual 
reproduction.  The  following  principle  has  been  formulated 
as  a  result  of  extensive  experiments  with  a  number  of  species: 
"Sexual  reproduction  can  be  attained  by  the  plant  only 
when  it  is  exposed  to  a  specifically  favorable  length  of  day 
(the  requirements  in  this  particular  varying  widely  with  the 
species  and  variety),  and  exposure  to  a  length  of  day  un- 
favorable to  reproduction  but  favorable  to  growth  tends  to 
produce  gigantism  or  indefinite  continuation  of  vegetative 
development,  while  exposure  to  a  length  of  day  favorable 
alike  to  sexual  reproduction  and  to  vegetative  development 
extends  the  period  of  sexual  reproduction  and  tends  to 
induce  the  '  ever-bearing'  type  of  fruiting. "  ^ 

67.  Biennial  bearing, — The  biennial  bearing  habit  of 
fruit  varieties  has  long  been  recognized  and  its  solution 
constitutes  an  important  practical  problem.  It  was  formerly 
considered  to  be  an  immutable  varietal  characteristic,  but 
this  view  has  been  radically  changed  and  it  is  now  regarded 
as  a  nutritional  problem.  This  conception  is  practically 
nccessaiy  inasmuch  as  there  is  no  biennial-bearing  commer- 
cial variety  which  has  not  been  shifted,  in  some  instance,  to 
annual  bearing  through  cultural  means.  That  the  problem 
is  nutritional  seems  evident,  even  though  treatments  ap- 
parently the  same  have  not  brought  about  annual  bearing 
in  all  orchards  of  the  same  variety.     It  must  be  conceded, 

1  Garner,  W.  W.,  o.nd  H.  A.  Allard.  Jour.  Agr.  Res.  Vol.  18,  No.  11. 
1920. 


72  POMOLOGY 

however,  that  some  varieties,  more  than  others,  are  incUned 
to  estabUsh  as  a  habit  either  amiual,  biennial,  or  irregular 
bearing. 

Roberts  ^  has  pointed  out  that  there  is  a  close  relation- 
ship between  fruit-bud  formation  and  spur  growth.  For 
example,  with  the  Wealthy  apple  under  Wisconsin  conditions, 
fruit-buds  are  formed  freely  when  the  spurs  make  a  growth 
of  one-eighth  to  three-eighths  of  an  inch  in  length,  and  when 
the  growth  is  much  less  or  greater,  flowering  is  partially  or 
entirely  suppressed.  In  the  "off"  year  when  85  or  90 
per  cent  of  the  spurs  formed  fruit-buds,  this  amount  of 
growth  was  common,  but  in  the  "on"  year  it  was  consistently 
shorter,  thus  producing  a  cycle  or  a  biennial  bearing  condition. 
This  observation  is  comparable  to  the  one  already  discussed, 
namely,  the  alternation  in  size  of  leaves  in  the  "on"  and 
"off"  years  with  the  Yellow  Transparent  (and  other) 
apples.  While  a  crop  of  fruit  usually  checks  vegetative 
extension,  leaf  size,  and  often  fruit-bud  formation,  such 
check  may  also  be  due  to  other  causes,  such  as  the  weather 
or  cultural  conditions,  and,  therefore,  it  is  not  necessary  for 
a  heavy  crop  of  fruit  to  precede  the  establishment  of  the 
biennial  bearing  habit. 

As  a  practical  solution  of  this  problem,  three  possible 
procedures  may  be  suggested.  First,  when  the  trees  are 
fruiting  heavily  and  consequently  making  less  than  the 
requisite  growth  (say  less  than  one-eighth  to  three-eighths 
inches) ,  the  trees  might  be  stimulated  by  an  early  application 
of  available  nitrogen.  Thinning  the  fruit  has  not  proved 
effective  in  accomplishing  this  result,  as  explained  in  Chapter 
VI.  Second,  during  the  off  year  when  the  growth  is  such  as 
to  be  conducive  to  flower  formation,  nitrogen  may  be  added 
in  order  to  push  the  trees  into  an  "  over  vegetative  "  condition 

1  Roberts,  R.  H.  Off-year  apple  bearing.  Wis.  Agr.  Exp.  Sta. 
Bull.  318. 


FRUIT-BUD  FORMATION 


73 


and  hence  reduce  fruit-bud  formation.  This  would  bring 
about  a  production  of  fewer  fruit-buds  but  greater  likelihood 
of  annual  bearing.  Third,  when  the  trees  are  habitually 
"over  vegetative,"  they  may  be  checked  until  they  are  in 
the  condition  for  fruitfulness. 


Class  A 

—  \  inch 
'On      year" — add      N 
early  in  season  to  stim- 
ulate greater  shoot 
growth 


Class  B 
i  to  I  inch 
'Off  year" — add  N.  to 
force,  greater  growth 
and  thus  reduce  the 
number  of  spurs 
which  produce  fruit- 
buds 


Class  C 
+  f  inch 
"Off  year" — seed  down 
to  grass,  ehminate  N. 
fertihzer  and  water 


In  other  words,  the  problem  is  practically  identical  with 
that  outlined  earUer  in  the  Classes  I  to  IV. 


^'V 


\^ 


CHAPTER  V 
PRUNING 

The  pruning  of  plants  received  attention  by  the  earliest 
writers  on  horticultural  subjects,  and  throughout  the  lit- 
erature of  horticulture  it  has  a  very  prominent  place.  The 
instruction  or  advice  given  consisted  largely  in  detailing 
methods  to  pursue  in  order  to  obtain  the  ideally  shaped 
tree  and  hence  was  concerned  with  the  art  of  pruning 
rather  than  with  the  effect  on  the  functions  of  the  plant. 
The  European  literature  on  the  subject  is  voluminous  and 
is  usually  accompanied  by  well-prepared  drawings  of  the 
various  methods  employed.  Much  of  the  present  teaching 
in  this  country  can  be  traced  to  that  source.  The  European 
gardeners  have  often  gone  to  extremes  in  training  trees  into 
unusual  forms  and  this  in  particular  has  found  its  way  into 
the  literature  of  that  continent.  In  commenting  on  the 
extent  to  which  tradition  has  influenced  the  opinions  in 
regard  to  pruning,  Bedford  and  Pickering  aptly  say:  "Prun- 
ing as  an  art  does  not  lend  itself  very  freely  to  scientific 
investigation  and  where  scientific  investigation  can  be 
brought  to  bear  on  it  the  teachings  of  the  artist  have  not 
always  been  confirmed. "  ^ 

It  is  only  comparatively  recently  that  experiments  planned 
in  sufficient  detail  have  been  undertaken  to  study  the  effect 
of  pruning  on  the  nutrition  of  the  tree  and  even  now  it 
cannot  be  said  that  there  is  full  agreement  as  to  the  re- 
sponses that  result.    The  art  of  pruning  is  interwoven  with 

1  Science  and  Fruit  Growing.  Macmillan  and  Co.,  London.  1919. 
p.  57. 

74 


PRUNING  75 

the  science  of  pruning  and  the  practice  requires  a  knowl- 
edge of  the  functions  of  the  tree  and  its  fruitiag  charac- 
teristics, as  well  as  judgment,  imagination,  and  forethought. 

68.  Definition. — Pruning  may  be  defined  briefly  as  the 
art  and  science  of  cutting  away  a  portion  of  the  plant  to 
improve  its  shape,  to  influence  its  fruitfulness,  to  improve  the 
quality  of  the  product,  or  to  repair  damage. 

69.  Objects  of  pruning. — ^The  objects  are  essentially 
two:  first,  to  change  the  shape  or  growth  of  the  tree  itself; 
and  second,  to  influence  the  production  and  the  character  of 
the  product.  Such  pruning  as  is  necessary  to  repair  damage 
is  largely  due  to  accident,  disease,  or  neglect.  It  is  easily 
possible  to  over-emphasize  the  importance  of  training,  for 
the  object  of  pruning  a  fruit-tree  is  certainly  not  alone  to 
produce  a  beautiful  or  shapely  object,  but  rather  to  obtain 
a  tree  that  is  commercially  profitable  and  capable  of  carrying 
its  crop  without  breakage  of  limbs.  It  is  not  uncommon, 
in  sections  where  apple  trees  grow  large  (as  in  western  New 
York) ,  for  them  to  produce  a  crop  weighing  as  much  as  a  ton 
and  a  half,  and  the  ability  of  the  tree  to  cany  such  a  load 
must  be  a  matter  of  foresight  by  the  orchardist.  Further- 
more, the  proper  pruning  of  a  tree  will  facilitate  other 
orchard  operations,  such  as  spraying  and  picking.  From  an 
orchardist's  viewpoint,  it  is  evident  that  pruning  has  a 
commercial  objective,  for  the  grower  desires  to  obtain  the 
most  return  from  the  least  outgo.  It  must  be  remembered, 
however,  that  the  most  return  is  not  always  commercially 
best,  as  is  pointed  out  more  fully  in  Chapter  VI.  This 
then  leads  to  an  adaptation  of  tree  type  to  conform  with 
other  orchard  practices,  which  in  themselves  must  be  adapta- 
tions to  enviromnent,  variety  characteristics,  and  the  like, 
and  it  is  this  ensemble  of  inter-acting  factors  that  influence 
the  tree,  or  rather  the  tree  and  its  product  are  the  organic 
result  of  all  of  this  inter-action. 


76 


POMOLOGY 


70.  Shape  or  form  of  the  tree. — The  general  shape  or 
form  of  a  tree  is  hirgely  a  varietal  character  and  is  not  easily 
changed.  A  tree  upright  in  habit  of  growth,  such  as  the 
Wealthy  or  Sutton  apple,  cannot  be  made  to  develop  into  a 
strictly  spreading  type  by  any  system  of  pruning.  Likewise 
a  tree  of  a  spreading  habit,  such  as  the  Rhode  Island  Green- 
ing, or  one  drooping  as  the  Wolf  River,  cannot  profitably  be 
changed  into  an  upright  growing  one  by  pruning  or  training. 
It  is  true,  however,  that  they  can  be  modified  to  some  degree 


a 

h 

c 

d 

Open  center 
All  growing 

Delayed 

Leader 

Two  story 

open  cen- 

Lower 

equally  due 

ter  or 

branches 

to  cutting 

modified- 

suppressed 

upper  branches 

leader 

because  of 

just  enough" 

lack  of 

harder  to 

terminal 

offset  advan- 

position 

tage  of      _  . 

upper  position 

Fig.  23. — Diagrammatic  representation  of  arrangement  of  scaffold 
limbs  in  pruning. 

by  pruning.  These  forms  or  shapes  of  trees  are  of  some 
taxonomic  value  and  in  many  cases  afford  a  ready  means  of 
recognizing  a  variety. 

71.  The  type  of  tree  to  be  developed  refers  directly  to 
the  placing  and  spacing  of  the  scaffold  limbs  on  the  body 
and  not  to  the  general  shape,  although  the  two  are  inter- 
related. There  are  several  forms  into  which  a  tree  may  be 
trained,  although  the  type  to  be  adopted  will  often  depend 
on  the  variety. 


PRUNING  77 

The  principal  forms  into  which  the  young  tree  may  be 
trained  are :  the  vase  or  open-headed ;  the  delayed  open  center 
or  modified  leader;  the  central  leader  or  pyramidal  type;  and 
the  two-story.^  The  vase-shaped  tree  is  developed  by  select- 
ing usually  from  three  to  six  scaffold  limbs  that  are  to  be 
somewhat  equal  in  importance  and  all  of  which  are  lateral 
branches  from  the  main  stem  or  trunk,  the  central  leader 
being  removed  at  planting  time.  These  scaffold  branches  are 
usually  cut  back  to  4  to  8  or  10  inches  in  length  at  the  time  of 
planting,  provided  the  tree  is  two  years  old.  If  one  year  old, 
the  top  is  cut  back  to  20  to  30  inches  in  height  and  the  scaffold 
branches  are  selected  from  the  initial  ones  sent  out  during  the 
ensuing  summer,  or  the  following  spring  when  they  receive 
their  first  pruning  and  training.  These  branches  are  selected 
radially  about  the  stem,  with  no  two  opposite  each  other,  the 
idea  here  being  that  even  cutting  of  these  selected  branches 
will  result  in  approximately  even  growth.     Fig.  23,  a. 

The  delayed  open  center  or  modified-leader  type  of  tree  is 
essentially  different,  in  that  the  central  leader  is  not  removed 
at  planting  time,  but  is  allowed  to  remain  and  grow  some 
three  or  four  feet  higher  than  the  scaffold  in  the  vase- 
shaped  type.  The  terminal  is  then  removed  to  prevent  a  full 
leader  tree  from  being  formed.  Along  this  axis  the  scaffold 
branches  are  chosen,  giving  a  better  spacing  and  more 
scaffolding  than  in  the  open  center  tree.  The  value  of  this 
type  is  that  the  side  or  scaffold  limbs  are  more  strongly  built 
and  not  so  likely  to  be  broken  out  by  a  heavy  crop  as  in  the 
case  of  the  vase-shaped  tree;  it  is  gaining  in  favor  in  many 
sections  of  the  East.  The  chief  objection  is  that  the  grower  is 
likely  to  allow  too  many  branches  to  remain,  resulting  in  a 
dense  tree  with  all  its  attendant  difficulties.    Fig.  23,  h. 

'  In  addition  to  these  four  general  types  of  training,  the  natural  or 
unpruned  tree  should  perhaps  be  included,  although  this  sort  of  neglect 
is  not  common  in  commercial  orchards. 


78  POMOLOGY 

The  leader  or  pyramidal  type  has  a  continuous  central  axis 
from  which  its  limbs  are  developed,  much  as  in  the  pines. 
The  limbs  are  strongly  attached  and  the  loss  of  any  individual 
scaffold  branch  is  of  slight  importance  compared  with  the 
same  loss  in  an  open  tree,  but  it  is  not  so  desirable  as  the 
semi-leader  or  delayed  open  center  tree.  The  branches  in 
such  a  tree  also  are  likely  to  crowd,  and  the  resulting  fruit  is 
often  small  and  of  poor  color.    Fig.  23,  c. 

The  "two-story"  tree,  so  called  because  it  has  one  distinct 
set  of  scaffold  branches  superimposed  over  another,  is  in  use 
in  some  orchard  regions  and  has  its  advocates.  This  type  has 
the  advantage  of  a  large  bearing  surface  and  strongly  at- 
tached limbs.  However,  the  limbs  of  the  upper  scaffold  may 
hang  down  over  those  of  the  lower  and  make  proper  pruning 
difficult.  Unequal  growth  of  one  or  the  other  of  the  sets  of 
branches  may  result  in  a  dwarfing  and  ultimate  starving  of 
the  weaker  ones.  These  conditions  should  be  carefully 
guarded  against  and  a  wise  selection  of  limbs  about  the 
entire  length  of  the  central  axis,  rather  than  two  distinct  sets 
of  scaffold  branches,  would  do  much  to  prevent  these  ob- 
jections.   Fig.  23,  d. 

72.  Obtaining  the  ideal. — Anyone  who  has  attempted  to 
train  a  block  of  trees  into  a  form  chosen  as  the  pattern  has 
learned  that  it  is  impossible  to  secure  uniform  results  with 
all  the  trees.  Some  varieties  are  much  more  difficult  to  train 
than  others  and  the  orchardist  can  only  adhere  as  closely  to 
his  ideal  as  the  growth  of  the  trees  will  permit. 

73.  Fruiting  system  of  the  tree. — Fundamental  to  any 
pruning  method  must  be  a  clear  understanding  of  the  habit  of 
the  tree  in  fruit-bearing.  This  subject,  however,  has  been 
discussed  for  the  various  fruits  in  a  foregoing  chapter  and 
need  not  be  repeated  here. 

74.  Effect  of  pruning  on  size  and  development  of  trees.^ 
It  is  conceded  that  the  form  of  the  young  tree  is  of  great 


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Plate  II. — a,  An  open-headed  apple  tree,    b,  A  two-story  apple  tree 
with  sets  of  scaffolds  too  close  together. 


PRUNING  79 

importance  and  pruning  should  be  performed  in  such  a  way 
as  to  produce  the  best  type  of  tree  when  it  reaches  maturity. 
Having  decided  on  the  form  desired,  the  question  arises  as  to 
the  general  effect  of  pruning  on  the  size  of  the  tree.  The 
position  of  many  writers  has  been  that  heavy  dormant 
pruning  increases  vegetation  and  that,  in  order  to  secure  the 
best  specimen,  rather  severe  pruning  should  be  practiced. 
More  recently,  however,  the  inaccuracy  of  this  statement  as 
a  general  conclusion  has  been  pointed  out,  although  it  is 
conccival)le  that  the  total  response  in  wood  growth  might 
not  be  influenced  so  much  under  some  conditions  as  under 
others  and,  therefore,  a  lack  of  full  agreement  on  this  point 
may  develop  in  the  literature.  The  reason  for  the  dwarfing 
effect  is  suggested  in  a  later  paragraph. 

The  results  have  varied  somewhat  when  young  trees — one 
to  three  years  old — have  received  heavy  and  light  pruning, 
but  with  older  trees  the  data  available  at  this  time  make 
possible  rather  uniform  conclusions. 

Alderman  and  Auchter^  conducted  an  expermient  in  West 
Virginia  with  trees  of  varying  age  and  found  that  the 
j^ounger  ones  produced  greater  growth  when  pruned  heavily, 
but  after  the  third  year  the  lightly  pruned  ones  grew  the 
most.  (Plate  IV.)  The  general  conclusion  from  this  work 
was  that  a  tree  produces  new  growth  in  inverse  ratio  to  the 
amount  of  wood  removed.  The  following  table  presents  a 
digest  of  the  data: 

1  The  apple  as  affected  by  varying  degrees  of  dormant  and  seasonal 
pruning.    W.  Va.  Agi.  Exp.  Sta.  Tech.  Bull.  158.    1916. 


80 


POMOLOGY 


Table  IX 


RESULTS  ON   GROWTH   OF  LIGHT  AND   HEAVY   PRUNING   OF  YOUNG   APPLE 

TREES    (stark) 


(after  ALDERMAN  AND  AUCHTER) 

1.911 

191^ 

1:>13 

1014 

1.9  Id 

Height 
in  ft., 
1,915 

Wid'h 
in  ft., 
1915 

Diam. 
trunk, 

una 

Average 

total  length 

of  growth 

in  feet 

Heavy  pruning 

4.41 

10.25 

41.53 

84.08 

101.74 

7.57 

5.17 

2.17 

Light  pruning 

5.58 

15.51 

34 .  33 

99 .  39 

224  89 

10.79 

G ,  85 

2.91 

The  same  observation  has  been  made  with  regard  to  bear- 
ing trees.  ^  After  twelve  years'  work  with  dwarf  apples  (the 
trees  were  then  fifteen  years  old),  they  were  lifted  and 
weighed,  with  the  following  observations :  "Those  which  had 
not  been  primed  at  all  were  20  per  cent  heavier  than  those 
which  had  been  moderately  pruned,  while  those  which  had 
been  hard-pruned  were  16  per  cent  lighter  .  .  .  thus  pruning 
not  only  doesn't  increase  the  actual  size  of  the  tree,  but  it 
results  in  less  new  wood  being  formed." 

Tufts  -  shows  that  there  is  a  definite  correlation  between 
trunk  circumference  and  the  weight  of  both  top  and  root 
development  of  two-year-old  black  walnut  and  almond 
seedlings.  Also  that  the  average  increase  in  circumference  of 
severely  pruned  apricot,  cherry,  peach,  pear,  and  plum  during 
four  seasons  was  8.9  centimeters,  moderately  pruned  10  9, 
and  lightly  pruned  12.3.  The  latter  developed  stockier  and 
stronger  branches  and  made  greater  development  than 
heavily  pruned  trees. 

Gardner  ^  also  points  out  that  unpruned  young  trees,  on  the 
average,  increased  in  size  as  rapidly  or  more  so  than  either 
dormant  or  summer  pruned  ones. 


1  Bedford  and  Pickering.    Woburn  Exp.  Fruit  Farm,  7th  Rept. 

2  Tufts,  W.  P.    Calif.  Agr.  Exp.  Sta.  Bull.  313.     1919. 

3  Ore.  Agr.  Exp.  Sta.  Bull.  139.    Pages  3-45.     1916. 


1907. 


PRUNING 


81 


Chandler  ^  reports  on  young  apple  and  peach  trees  of 
different  ages  with  the  same  general  results  as  above  indi- 
cated, and  the  data  from  the  one-year  old  nursery  stock 
may  be  taken  as  typical  of  the  results.  The  trees  were 
selected  carefulty  as  to  uniformity  of  size  and  a  part  of  them 
had  their  opening  buds  removed  from  the  trunks  to  a  height  of 
about  18  inches,  while  the  remainder  were  untreated.  At  the 
end  of  the  season,  the  following  data  were  obtained : 


Table  X 

ON  PRUNING  ONE-YEAR-OLD  DELICIOUS  TREES    (aPTER  CHANDLER) 


Treahucnt 

Number 
of  trees 

Ave.  number 
of  leaves, 
Oct.  19 

Wt.  of  tops, 
grams, 
Oct.  19 

Wt.  of  roots, 
grams, 
Oct.  19 

Pruned 

Unpruncd. .  .  . 

16 
14 

149 
272 

168.2 
236.6 

24.0 
33.2 

Reference  has  been  made  to  sufficient  experiments  to 
indicate  the  status  of  the  subject  at  this  time,  and  while  it 
would  seem  that  practically  all  pruning  is  a  dwarfing  process, 
it  should  not  prejudice  the  student  against  the  necessity  of 
such  training  of  the  young  tree  or  pruning  of  the  old  one  as  is 
necessary  for  the  securing  of  a  well-balanced  and  fruitful 
individual. 

75.  Effect  of  pruning  on  early  bearing. — Of  still  greater 
importance  to  the  orchardist  is  whether  heavy  pruning  of 
young  trees  will  hasten  or  delay  their  coming  into  commercial 
bearing.  In  this  connection  it  must  be  remembered  that 
blossoming  does  not  necessarilj^  mean  fruit  production.  In 
general,  it  seems  well  established  that  the  less  pruning,  the 
sooner  a  tree  will  form  fruit-spurs  and  fruit-buds  and  es- 
tablish the  bearing  habit.  It  does  not  necessarily  follow 
^  Proc.  Amer.  Soc.  Hort.  Sci.    1919. 


82 


POMOLOGY 


that  heavy  pruning  may  not  be  conducive  to  greater  fruit 
production  on  an  older  tree,  as  is  pointed  out  in  paragraph  79. 

This  idea  is  not  new  but  has  frequently  been  mentioned  by 
early  writers.  In  1768,  Hitt  wrote  as  follows:  "If  there  are 
two  apple,  pear,  plum  or  cherry  trees,  equal  in  health  and 
strength,  at  one  year  old  after  grafting,  let  them  remain 
some  years  after  in  the  same  stations  .  .  .  and  one  of  them 
be  pruned,  and  the  other  not,  but  suffered  to  grow  in  a  shape 
quite  rude  and  natural,  the  latter  will  produce  fruit  much 
earlier  than  the  other,  though,  perhaps,  its  branches  will  not 
be  in  so  regular  a  position  as  those  of  the  former;  hence  it  may 
be  reasonably  inferred  that  premature  pruning  a  healthy, 
strong  standard,  in  what  manner  soever,  before  blossoming, 
will  keep  it  longer  back  from  a  bearing  state  than  it  would  be 
were  it  left  unpruned."  ^ 

This  effect  of  pruning  on  early  bearing  is  shown  by  work  at 
Woburn  on  dwarf  apple  trees.  Records  for  twelve  years  were 
reported  in  three  periods,  wherein  the  yield  of  moderately 
pruned  trees  was  given  a  value  of  100  and  the  other  treat- 
ments compared  with  it,  as  follows : 


Table  XI 

EFFECT   OF    PRUNING    ON   EARLY   BEARING    (wOBURN) 


Id  5  yrs. 


2d  5  yrs. 


12th  year 


Heavy  pruning .  .  . 
Moderate  pruning 
Light  pruning. .  .  . 
No  pruning 


75 
100 

90 
220 


50 
100 
150 
200 


100 
145 
275 


Similar  results  were  obtained  by  Alderman  and  Auchter 
with  young  trees  just  coming  into  bearing,  as  shown  by  the 
following  data: 

'  Hitt,  Thomas.    A  Treatise  of  Fruit  Trees.    3d  Ed.    London,  1768. 


PRUNING 


83 


Table  XII 

EFFECT  OF  PRUNING  ON  EARLY  BEARING  (AFTER  ALDERMAN  AND  AUCIITER) 


Type  of 
pruning 

Bloom 

clusters 

to  a  tree, 

1914 

Fruits 

to  a  tree, 

1914 

Bloom 

clusters 

to  a  tree, 

1915 

Fruits  to  a 
tree,  1915 

Percent- 
age fruit- 
buds  to 
a  tree, 
1916 

No. 

Wt.,  lbs. 

.14 
3. -4 
15.5 

0 
2 

2.0 

1.86 
40.00 
175.00 

.7 
12.2 
24. 

.25 
3.35 
6. 04 

3.7 

Moderate 

Light 

20. 

38. 

In  these  experiments,  more  mature  trees  were  also  treated 
with  the  result  that  the  heaviest  pruned  yielded  more  fruit 
than  the  lightly  pruned  ones.  However,  the  trees  were 
reported  as  in  poor  condition  (making  only  four  inches  of 
terminal  growth)  and  hence  the  data  are  not  considered  so 
relial^le  as  in  the  cases  of  younger  trees. 

76.  Effect  of  the  unequal  cut. — A  common  weakness 
in  the  framework  of  the  tree  is  a  sharp-angled  crotch  or 
fork  wherein  one  branch  of  the  fork  is  about  equal  to  the 
other  in  size.  This  produces  a  condition  which  is  likely 
later  to  result  in  a  poor  type  of  development  and  a  breaking 
of  the  tree.  This  can  be  avoided  by  the  "unequal  cut"; 
that  is,  by  not  cutting  back  the  two  branches  of  such  a  fork 
equally,  but  by  making  one  decidedly  shorter  than  the  other 
so  as  to  suppress  its  development  and  make  it  subordinate 
to  the  longer  one  which  becomes  a  leader.  By  this  method, 
a  much  stronger  tree  can  be  built. 

On  first  thought  this  principle  would  not  seem  to  be  in 
harmony  with  the  obsei-ved  fact — which  is  discussed  later— 
that  there  is  a  stimulation  to  vigorous  growth  at  the  point 
where  the  cut  is  made.  An  explanation  seems  available, 
however,  to  account  at  least  in  part  for  the  effect  of  the  vni- 
equal  cut.    The  case  is  at  once  different  from  one  in  which 


84 


POMOLOGY 


the  entire  top  of  the  tree  is  pruned.  When  only  a  few  shoots 
are  cut  back,  there  is  no  measurable  unbalancing  of  the 
root  system  and  top  of  tree  and,  therefore,  no  excessive  supply 
of  water  and  soil  nutrients,  for  the  other  branches  of  the 
tree  will  make  use  of  any  additional  amount.  As  a  result, 
no  special  stimulation  is  manifest  and  the  branch  which  was 
pruned  is  reduced  in  size  in  comparison  with  its  former 
rate  of  growth. 

The  following  experiment  may  be  cited  on  this  point:  ^ 
A  shoot  of  equal  length  was  chosen  for  observation  on  a 
number  of  three-year-old  nursery  trees.  This  shoot  was  cut 
back  one-third  its  length  in  all  cases,  but  with  half  the  trees 
under  observation  all  the  other  branches  were  likewise 
pruned  back.  The  answer  to  the  question  here  involved 
will  depend  on  whether  the  selected  shoots  will  respond 
similarly  on  both  blocks  of  trees.  The  following  data  show 
that,  if  the  remainder  of  the  tree  is  pruned,  the  selected 
shoot  makes  a  much  greater  growth  than  if  it  is  the  only  one 
which  is  cut: 

Table  XIII 

NURSERY  STAYMAN  WINESAP,   1919    (AFTER  CHANDLER) 


Treatment 

Number 
of  trees 

Ave.  twig 
length,  inches, 
before  pruning, 
May  23,  1919 

Ave.  twig 
length,  inches, 
after  priming, 
May  23,  1919 

Inches  of 

new  growth 

from  each 

pruned  twig, 

Sept.  20,  1919 

Tree  pruned .  . 
Tree  unpruned 

30 
30 

29.2 
29.2 

9.9 
9.9 

32.0 
9.9 

77.  Heading-back  versus  thinning-out. — In  discussing 
the  effect  of  pruning  on  the  size  and  development  of  trees, 
no  differentiation  was  made  between  types,  but  rather  the 

1  Chandler,  W.  H.    Proc.  Amer.  Soc.  Hort.  Sci.    1919.    pp.  88-101. 


PRUNING  85 

general  bulk  pruning  was  treated,  consisting  in  both  head- 
ing-back and  thiiming-out  of  the  young  trees.  The  effects 
of  these  two  types  of  pruning  on  the  branch  growth  and 
the  development  of  fruit-spurs  may  now  be  studied  to 
advantage. 

Heading-back  refers  to  the  cutting  of  the  shoot  or  branch, 
removing  the  terminal  growing  point  and  a  certain  number 
of  the  lateral  buds  or  shoots  nearest  the  end  of  the  branch. 

Thimiing-out,  on  the  other  hand,  means  the  removal  of 
surplus  branches  or  shoots  without  any  heading-back  proc- 
ess. The  effects  of  these  two  types  of  pruning  are  different 
and  should  be  carefully  examined. 

The  experiments  of  Gardner  ^  in  Oregon  were  so  arranged 
that  the  responses  to  these  two  types  of  pruning  could  be 
studied  in  detail.  They  show  in  general  that  thinning-out 
is  more  favorable  to  fruitfulness  than  heading-back,  al- 
though both  practices  would  be  included  in  orchard  oper- 
ations. The  general  response  from  the  total  or  bulk  pruning 
was  not  entirely  in  accord  with  the  experiments  cited  above, 
in  discussing  the  effect  of  pruning  on  size  of  tree,  but  varieties 
varied  to  a  considerable  degree.  With  Grimes  on  Doucin 
roots  it  made  little  difference  whether  a  shoot  was  left  un- 
pruned  or  was  headed-back  lightly  or  severely,  the  subse- 
quent units  of  growth  the  following  season  being  about  the 
same.  The  number  of  shoots  resulting  if  a  branch  was 
severely  headed-back  would,  however,  be  fewer  than  if 
lightly  headed-back  or  left  unpruned.  With  the  varieties 
Esopus,  Rome,  and  Gano,  on  the  other  hand,  heavy  pruning 
checked  their  growth.  These  latter  statements  refer  to  the 
effect  of  pruning  on  the  subsequent  size  of  the  tree  and  are 
not  to  be  confused  with  those  in  regard  to  the  development 
of  spurs  and  fruit-buds  when  trees  are  headed-back  or 
thimied-out. 

'  Ore.  Agr.  Exp.  Sta.  Bull.  139.    pp.  3-^5. 


86  POMOLOGY 

With  all  the  trees  in  the  experiments,  heading-back 
resulted  in  a  decrease  in  the  number  of  fruit-spurs  to  which 
the  individual  shoot  gave  rise,  this  being  more  marked  with 
increase  in  the  severity  of  the  heading.  In  other  words, 
fruit-spur  formation  on  the  individual  shoot  was  correlated 
with  its  length  after  rather  than  before  the  pruning. 

A  statistical  study  of  the  two  types  of  pruning  as  applied 
to  Grimes,  Gano,  Rome,  and  Esopus  seemed  to  warrant 
the  following  conclusions: 

1.  A  general  heading-back  of  the  shoots  of  a  tree  acted  as 
a  stimulus  to  new  growth.  The  amount  of  the  stimulus 
varied  considerably  with  variety. 

2.  An  equally  severe  thinning  acted  as  a  check  to  new 
growth,  but  this  also  varied  somewhat  with  variety. 

3.  Heading-back  resulted  in  a  more  marked  check  to 
fruit-spur  formation  than  did  equally  severe  thinning-out, 
with  such  varieties  as  Grimes  and  Esopus.  The  reduction 
was  not  so  marked  with  Gano  and  Rome,  as  they  bear  a 
large  percentage  of  their  fruit-buds  laterally  on  the  new, 
terminal  shoots,  especially  when  young. 

4.  Thimiing-out  increased  the  production  of  fruit-spurs, 
as  compared  with  equally  severe  heading.  On  the  other 
hand,  heading  generally  augmented  the  production  of  ter- 
minal fruit-buds  on  the  few  shoots.  In  some  varieties, 
thinning  was  accompanied  by  a  greater  production  of  lateral 
fruit-buds  on  shoots  than  equally  severe  heading;  in  other 
varieties,  the  reverse  was  the  case.  In  general,  thinning- 
out  tends  to  increase  flower  and  fruit  production,  while  the 
heading-back  is  likely  to  decrease  those  functions. 

These  two  types  of  pruning  are  further  considered  in  detail 
as  they  a]5ply  to  young  trees. 

78.  Detailed  response  of  young  trees. — As  is  described 
and  discussed  above,  thinning-out  refers  to  the  removal  of 
a  portion  of  the  limbs,  branches  or  shoots  in  order  to  "open 


PRUNING  87 

up  "  the  tree  and  is  essentially  different  from  heading-back, 
inasmuch  as  the  ends  of  shoots  or  branches  are  not  cut  off. 
As  a  result,  the  terminal  bud  continues  the  growth  of  the 
branches  and  the  lateral  buds  usually  develop  into  branches 
or  spurs  or  remain  dormant.  Gardner  has  calculated  on 
this  basis  that  of  100  shoots  bearing  ten  lateral  buds  each 
and  also  a  terminal  bud  in  this  case,  a  light  thinning  out 
(30  per  cent)  would  leave  770  buds— 700  lateral  and  70 
terminal.  It  was  then  assumed  that  from  these  70  shoots 
"we  obtain  140  shoots  and  490  spurs,  leaving  140  dormant 
buds,"  which  is  considered  not  far  from  what  would  actually 
be  obtained.  From  a  heavy  thinning-out  (60  per  cent)  of 
this  same  number  of  shoots  there  would  be  40  untouched 
ones.  These  would  probably  behave  in  much  the  same 
manner  as  the  branches  on  the  lightly  thinned  tree.  ''Were 
this  the  case  the  result  would  be  eighty  new  shoots  (forty 
from  the  terminal  buds  and  forty  from  as  many  lateral  buds), 
about  three  hundred  twenty  spurs,  and  forty  dormant  buds. 
The  individual  spurs  would  be  thicker  and  more  vigorous 
in  appearance,  but  probably  the  proportion  of  buds  to  develop 
into  fruit-spurs  would  remain  about  the  same."  Thus  a 
light  thinning-out  gives  more  shoots  and  fruit-spurs  than  a 
heavy  one. 

The  results  of  this  estimate,  based  on  extensive  observation 
and  experiment,  are  summarized  in  Table  XIV. 


88 


POMOLOGY 


Table  XIV 

PROBABLE   RESULTS   FROM   DIFFERENT   METHODS   OF   PRUNING   ONE   HUN- 
DRED   SHOOTS,    EACH   HAVING   TEN   EQUALLY   SPACED    LATERAL   BUDS 
(AFTER   GARDNER) 


11 
11 

11 

il 

Number  terminal  buds  left 

0 
700 
200 
300 
200 

0 

400 

250 

150 

50 

70 
700 
140 
490 
140 

40 

400 

Number  new  shoots  formed 

Number  spurs  formed 

80 
320 

Number  buds  remaining  dormant . .  . 

40 

Not  only  is  it  concluded  that  thinning-out  has  a  beneficial 
effect  on  fruit-spur  development,  but  also  on  their  vitality 
and  longevity.  The  trees  that  are  headed  back  have  a  strong 
development  of  new  shoots,  mostly  on  the  outside  and  top 
of  the  tree  and,  as  a  result,  the  spurs  on  the  inside  suffer 
and  become  non-productive,  if  indeed  they  do  not  die.  On 
the  other  hand,  thinning-out  tends  to  strengthen  the  spurs 
already  formed  as  well  as  to  develop  new  ones. 

79.  Relation  of  pruning  to  nutrition. — That  the  relation 
of  the  stored  food  materials  and  the  soil  nutrients  and 
moisture  may  be  profoundly  affected  by  pruning  as  well  as 
by  cultural  practices  has  been  emphasized  by  Kraus  and 
Kraybill.  Any  one  of  four  sets  of  conditions  may  be  en- 
countered, similar  to  those  described  in  Chapter  IV. 

1.  A  marked  reduction  in  or  limitation  of  carbohydrates, 
even  though  there  were  an  abundance  of  available  moisture 
and  nitrates,  would  result  in  a  depressed  vegetative  condition 
as  well  as  a  reduction  in  blooming  and  fruit  production. 
This  condition  would  result  from  heavy  pruning  as  well  as 
lack  of  photosynthetic  activity,  and,  therefore,  additional 


\J 


PRUNING  89 

pruning  would   have   a   tendency   to   restrict  furt.her  the 
growth  activity. 

2.  An  abundance  of  moisture,  nitrates,  and  carbohydrates 
would  result  in  rapid  vegetative  extension.  Under  these 
conditions,  it  is  probable  that  more  time  would 
be  required  to  manifest  a  dwarfing  of  the  tree 
by  pruning  than  when  one  or  more  were  lacking. 

3.  The  ideal  situation  would  exist  if  there 
were  present  or  available  a  moderate  Init  ample  ft  f 
amount  of  nitrogen,    together    with    carbohy-  ^\  ' 
drates,  in  case  the  latter  are  synthesized  in  excess  \^ 
of  the  quantities  utilized  in  vegetative  exten- 
sion,  that  is,  an   ample   reserve   food   supply 
would  be  present  within  the  tree.    The  result 
would  be  a  good  growth  and  a  rather  free  de-           ^  J  / 
velopment  of  reproductive  parts.      It  is  sug- 
gested that  pruning  may  or  may  not  be  needed, 
but  usually  some  is  required.    Pruning  would  fur- 
nish  a  ready  practical  means    of  regulating  the 
nitrogen-moistiu'e-carbohydratc  relation. 

4.  A  fourth  condition  is  frequently  encountered 
in  old  neglected  orchards  or  with  trees  damaged  in 
such  a  way  as  to  approximate  girdling.    In  such 
cases,  there  is  usually  a  depressed  vegetative  con- 
dition, the  trees  bearing  small  light-colored  leaves, 
and   they   may   or  may   not    produce   abundant 
blossoms  which  are  not  likely  to  "set"  well.     Fre- 
quently such  trees  contain  carbohydrates  in  excess, 
as  compared  with  the  availal)le  nitrate  nitrogen, 
or  moisture,  or  both.     In  order  to  effect  a  Fig.  24. 
balance  and  induce  vigorous  growth  and  bios-  Showing  the  type 
soms  capable  of  setting  fruit,  either  of  two    ^qj^^^q^i       rj!, 
procedures  might  be  followed  but  preferably    jo^^g  ^^^  cutting 
both.    Top-pruning  would  reduce  the  total    of  the  terminal. 


90 


POMOLOGY 


An  excess  of  either 
vigorous  growth 
80.  Theoretical 
importance  on 
must  have  as 
ground  a  body 
based  largely  on 
biochemical,  and 
analyses,  and  with 
bulky  to  handle 
mation  comes 
or  postulates  now 


relative  carbohydrates  and  hence  increase  the  relative  pro- 
portion of  moisture  and  nitrogen;  or  the  application  of  a 
quickly  available  form  of  nitrogen,  such  as  nitrate  of  soda 
or  sulfate  of  ammonia,  would  produce  the  desired  result, 
treatment  would  push  the  tree  into 
and  again  reduce  flowering. 
considerations. — Any  theory  of 
pruning 
its  back- 
of  facts 
chemical, 
physical 
plants  as 
as  fruit-trees  such  infor- 
slowly.  The  speculations 
available  can  scarcely  be  tenned 
theories,  but  recent  work  is  in 
material  advance  of  the  former 
"philosophy"  expressed  on  the 
suliject  and  the  near  future  will 
undoubtedly  reveal  much  of  fact 
that  is  now  lacking. 

Commonplace  as  pruning 
seems,  it  is  a  singular  practice. 
It  might  at  first  thought  be 
likened  to  the  thinning  of  plants 
which  are  growing  very  close 
together,  and  yet  it  is  funda- 
mentally different  because  the 
various  parts  of  the  tree  possess  a  single  or  common  root 
system.  Again,  the  branches  of  a  tree  seem,  in  many  ways, 
to  be  independent  units,  yet  they  are  members  of  a  single 
whole.  However,  all  the  different  parts  are  usually  not  so 
placed  as  to  be  favorable  to  high-grade  fruit  production  or 


Fig.  25.— 
Showing  a 
type  of  growth  that 
follows  when  the  ter- 
minal is  not  removed. 
The  buds  which  give 
rise  to  shoots  are  us- 
ually not  confined  to 
the  terminal  ones. 


PRUNING  91 

for  the  strongest  mechanical  structure.  If  this  dense  growth 
is  allowed  to  develop  unchecked,  it  will  result  in  an  excess 
shading  of  certain  parts  with  a  resultant  condition  that 
might  be  loosely  called  starvation,  followed  by  a  dying  of 
the  branches. 

If  limbs  or  branches  are  removed,  it  is  common  knowl- 
edge that  certain  shoots  are  likely  to  develop  which  would 
otherwise  remain  as  latent  buds,  and  especially  there  is  a 
stimulation  or  increased  cellular  activity  near  the  point 
where  the  cut  has  been  made.  This  response  on  the  part 
of  the  tree  is  a  type  of  regeneration — a  provision  through 
which  some  organisms  replace  lost  parts — which  leads  to 
the  point  here  involved :  why  or  how  does  the  plant  manifest 
this  increased  activity  near  the  point  of  injury?  See  Figs.  24 
and  25. 

One  theory  commonly  accepted  is  that  a  reduction  in 
the  number  of  growing  points  and  cambial  area  would  make 
available  to  the  remaining  parts  an  increased  amount  of 
the  tree's  reserve  food  supply,  from  which  at  least  the 
initial  growth  is  made.  With  this  increased  food  supply, 
the  opening  buds  would  make  a  much  greater  growth  than 
would  have  been  possible  had  no  growing  points  been  re- 
moved. 

A  second  theory  would  account  for  the  growth  response 
following  pruning  by  assigning  the  cause  more  particularly 
to  the  increase  in  amount  of  moisture  and  mineral  nutrients, 
particularly  nitrogen,  to  carbohydrates  that  are  made 
available  to  the  parts  remaining.  That  is,  it  is  due  to  a 
disturbance  in  the  balance  of  the  materials  within  the 
tree.    These  two  views  may  be  considered  briefly  together. 

In  the  first  place,  it  is  well  known  that  a  fruit-tree  usually 
manufactures  more  food  material  than  is  utilized  in  the 
various  phases  of  growth,  including  the  production  of  the 
crop.    The  unused  portion  is  translocated  downward  through- 


92 


POMOLOGY 


out  the  whole  tree  and  remains  in  the  cells  of  the  storage 
tissues;  it  is  termed  "reserve  material"  because  it  can  be 
used  later  in  growth. 

Secondly,  the  amount  and  form  in  which  the  reserves 
occur  in  the  parts  of  the  tree  vary  at  different  times  of  the 
year,  and  one  year  with  another.  The  following  table 
illustrates  this  point  by  showing  the  amounts  of  dry  matter, 
starch,  and  saccharose  at  time  buds  are  swelling,  in  case- of 
a  seven-year-old  Bismark  apple  tree  that  has  been  growing 
in  sod  for  four  years. 

Table  XV 

amounts  op  dry  matter,  starch,  and  saccharose  in  seven-year- 
old  apple  tree  at  time  buds  are  swelling 
(after  chandler) 


Part  of  tree 


Pounds 

Pounds 

Pounds 

dnj  wgt. 

starch 

saccharose 

3.15 

0.98 

.12 

21.00 

6.72 

.17 

15.13 

5.14 

.11 

14.15 

5.43 

.28 

6,49 

2.37 

.06 

1-year  twigs.  . 
Older  branches 

Trunk 

Large  roots .  .  . 
Small  roots .  .  .  . 


Furthermore,  it  is  significant  in  this  connection  to  note 
that  the  reserves  seem  to  be  lower  in  the  tree  in  spring  and 
early  summer  when  growth  is  very  active  than  at  other 
seasons,  indicating  that  they  are  utilized  in  growth.  It 
should  also  be  recalled  that  growth  activities  are  going  on 
within  the  tree  before  leaves  or  blossoms  are  put  forth. 
The  following  data  would  seem  to  establish  this  conception 
so  far  as  the  soluble  materials  are  concerned.  According 
to  Chandler,  the  freezing  point  of  the  sap  seems  to  be  a  fair 
measure  of  the  amount  of  soluble  carbon  compounds  present 
at  different  seasons: 


PRUNING 


93 


Table  XVI 


FREEZING    POINT    DEPRESSION    OF    BARK    SAP    OF    ELBERTA 
WILD  SWEET  CHERRY  TWIGS    (AFTER   CHANDLER) 

PEACH    AND 

Elberta  peach 

Wild  sweet  cherry 

1916 

Freezing 
point  de- 
pression, 
°C 

Moisture 

per- 
centage 

Freezing 
point  de- 
pression, 

°C 

Moisture 

per- 
centage 

March  25                     

3.010 
2.096 
1.880 
1.378 
1.540 
1.810 
2.158 
2.230 
2.233 
2.567 

59.2 

62.0 
54.6 

2.255 

1.485 
1.295 
1.120 
0.985 
1.553 
1.730 
1.763 
2.563 

At3iil  17 

May  3 

May  10 

60.1 

June  19 

July  6 

August  17        

61.4 

October  5 

December  29 

54.3 

According  to  Price/  the  starch  also  is  practically  ex- 
hausted in  the  early  growing  season  in  all  parts  of  the 
tree  above  the  ground.  If  these  statements  are  accepted, 
according  to  the  first  theory  there  should  be  no  stimulation 
if  the  pruning  is  done  at  the  beginning  of  the  growing  season. 
Chandler  has  shown,  however,  that  it  makes  no  difference 
whether  the  pruning  is  performed  during  the  growing 
season  or  in  late  spring,  so  far  as  growth  response  is  con- 
cerned. Hence  this  evidence  would  weaken  the  first  theory 
and  the  latter  calls  for  more  careful  attention. 

From. what  has  been  said,  it  would  seem  evident  that  any 
pruning  whatsoever  would  reduce  the  total  amount  of  re- 
serves available  for  future  growth.  However,  top-pruning 
will  also  reduce  the  future  leaf  area  that  is  to  maintain  the 

1  Price,  W.  A.    Ohio  Jour.  Sci.,  Vol.  16.    pp.  356-359.    1916. 


94  POMOLOGY 

synthesis  of  the  tree  and  hence  profoundly  disturb  its  re- 
lation with  the  amount  of  soil-moisture  and  nutrients 
taken  up  by  the  undisturbed  root  system.  To  what  extent 
a  reduction  in  the  top  of  the  tree  will  affect  the  amount 
of  water  and  mineral  nutrients  absorbed  by  the  roots  can- 
not be  stated  definitely  at  this  time,  but  certainly  each 
growing  point  remaining  must  receive  a  greater  supply 
than  had  no  pruning  been  practiced.  This,  then,  would 
seem  to  account  in  part  for  the  apparent  stimulation  to 
growth  which  takes  place. 

Critical  observation  has  shown  that  heavy  pruning  will 
result  in  dwarfing  of  a  tree,  as  already  noted.  This  is  ex- 
plained on  the  grounds  that  fewer  growing  points  must 
necessarily  produce  less  total  linear  growth  and  hence  less 
weight  and,  therefore,  the  top  of  the  tree  is  somewhat  re- 
duced. This  dwarfing  in  the  top  will  react  on  the  root 
system  and  it  will  become  restricted. 

81.  When  to  prune. — ^Divergent  views  have  been  held 
as  to  the  best  time  to  prune  fruit-trees,  but  careful  obser- 
vations are  bringing  about  more  unity  of  opinion.  An  old 
adage  says  ''Prune  when  the  knife  is  sharp,"  but  another 
admonishes  not  to  prune  frozen  trees  and  not  to  prune 
when  the  sap  is  "running";  so  the  layman  has  been  left 
somewhat  confused.  Little  actual  experimental  work  has 
been  done  along  these  lines  but  much  experience  may  dic- 
tate practice.  From  an  experiment  with  apple  trees  con- 
ducted in  Minnesota,  where  the  winter  temperatures  are 
low,  it  is  concluded  that  no  difference  in  the  healing  of  the 
wounds  resulted  whether  the  cutting  was  in  fall,  midwinter 
when  the  trees  were  frozen,  or  in  the  spring.^  With  hardy 
fruits  it  is  not  uncommon  to  prune  at  any  time  during  the 
dormant  season,  but  preferably  in  late  winter  or  early  spring. 
With  the  grape,  peach,  and  other  fruits  hable  to  winter  in- 
1  Brierley,  W.  G.    Proc.  Amer.  Soc.  Hort.  Sci.    1919.    p.  102. 


PRUNING  95 

juiy,  it  is  best  to  delay  pruning  until  severe  freezing  weather 
is  past.  In  Oregon  it  was  observed  that  whether  apples 
were  pruned  in  November,  i.  e.,  just  at  leaf  fall,  December, 
or  March  (when  buds  were  sweUing),  the  results  were  iden- 
tical. The  amount  and  type  of  pruning  was  far  more  im- 
]iorta-nt  than  ihc  tunc. 

82.  Pruning  at  planting  time. — Since  the  balance  between 
tlio  root  system  and  top  is  disturbed  when  trees  are  dug  for 
transplanting,  it  becomes  desirable  to  prune  the  tree  at 
planthig  time.  Occasionally  a  block  of  trees  is  seen  that  was 
not  pruned  when  planted  and  the  result  is  a  number  of 
small  growths  on  the  long  slender  branches,  making  it  al- 
most impossible  to  prune  with  any  satisfaction  at  a  later 
period.  Unless  the  moisture  conditions  are  very  favorable, 
many  of  such  unpruned  trees  are  likely  to  suffer  perma- 
nent damage. 

Dr.  Warder  once  said  that  the  hole  for  a  tree  should  be 
as  big  as  the  orchard.  If  his  advice  is  taken,  the  soil  well 
prepared  and  the  hole  made  large,  it  is  possible  to  plant 
without  reducing  the  root  system  more  than  is  done  in  dig- 
ging the  trees.  There  appears  to  be  no  virtue  in  reducing 
the  roots  to  mere  stubs  unless  they  are  broken  or  mangled, 
diseased,  or  seriously  dried  out.  Long  weak  roots  should, 
of  course,  be  made  to  conform  to  the  others  in  length  for 
convenience  in  handling.  The  first  new  growth  of  the  tree 
is  made  from  the  reserve  material  within  it,  but  as  soon  as 
the  leaves  appear  they  require  moisture  for  functioning. 
Therefore,  the  reduction  in  leaf  surface  through  pruning 
gives  the  roots  an  opportunity  to  develop  a  new  area  of 
root-hairs  more  nearly  proportional  to  the  leaf  surfaces  which 
are  instrumental  in  absorbing  the  soil-moisture. 

Some  extensive  tests  were  made  at  the  Woburn  Fruit 
Fann  to  determine  the  effect  of  careless  planting  on  the  after 
growth  of  the  trees.     The  results  were  surprising  in  most 


96  POMOLOGY 

respects,  as  they  showed  that  trees  carelessly  planted  and 
the  soil  rammed  about  the  roots  produced  a  greater  growth 
than  those  set  in  the  "orthodox"  way.  No  injurious  effect 
resulted  from  planting  trees  with  mangled  or  broken  roots, 
provided  a  reasonable  portion  of  the  root  system  was  left 
intact.  Neither  did  the  huddling  of  the  roots  into  a  small 
hole  have  any  apparent  effect.  The  conclusion  is  drawn  that 
trimming  of  the  roots  is  altogether  unimportant,  the  omis- 
sion having  sometimes  one  effect  and  sometimes  another.^ 

83.  Pruning  young  versus  mature  trees. — The  problem 
of  pruning  the  yomig  tree  is  essentially  different  from  that 
of  pruning  the  mature  one  so  far  as  purpose  is  concerned, 
but  the  basic  principles  remain  the  same.  In  the  first  place, 
the  great  essential  is  properly  to  select  the  future  scaffold 
branches  and  prune  consistently  to  develop  the  type  of  tree 
selected  as  the  ideal.  The  first  three  or  four  years  of  the 
apple  and  pear  and  the  first  two  years  of  the  peach  tree  rep- 
resent the  formative  or  vegetative  period  in  which  the  chief 
aim  of  the  grower  should  be  to  develop  a  well-formed  speci- 
men, regardless  of  fruit-spurs  or  buds.  The  tree  then  enters 
a  period  when  it  is  desirable  to  consider  the  growth  of  fruit- 
ing wood,  and  with  the  apple  and  pear  it  means  a  cessation 
of  a  systematic  cutting  back  of  the  terminals  and  usually  as 
little  pruning  as  possible.  This,  of  course,  does  not  mean  that 
small  rubbing  branches  and  water-sprouts  should  not  be 
removed  or  that  a  long  rangy  branch  should  not  be  sup- 


The  tree  next  passes  into  the  period  of  fruitage  when  the 
type  of  pruning  will  develop  very  largely  into  a  thinning- 
out  process  with  the  apple  and  pear  but  also  heading-back 
with  the  peach.  As  trees  of  the  former  fruits  become  older 
and  larger,  it  will  often  be  desirable  also  to  head-back  some 

^  Bedford,  Duke  of,  and  Spencer  Pickering.  Science  and  Fruit 
Growing.    London,  1919.    Ch.  4  and  5. 


PRUNING  97 

of  the  longest  and  highest  branches,  depending  on  the  vari- 
ety, distance  of  planting,  and  other  conditions  of  locality 
and  preference.  The  cherry  as  well  as  the  peach  should  be 
kept  pruned  to  an  open  tree  as  the  spurs  and  shoots  will  be 
more  fruitful  and  the  branches  more  vigorous.  The  same 
practice  should  also  be  followed  with  the  plum. 

84.  Salient  features  in  pruning  mature  trees.— The  fol- 
lowing points  should  be  borne  in  mind  by  the  pruner  in  han- 
dling mature  trees: 

1.  Remove  all  dead  branches,  also  diseased  or  injured 
parts  in  order  to  safeguard  the  remaining  portions  of  the 
tree.  Some  exceptions  to  this  may  be  noted  in  case  of  such 
a  disease  as  black-rot  canker  {Sphceropsis  malorum)  if  it  is 
abundant  through  the  tree.  If  all  diseased  limbs  were  re- 
moved, little  of  the  tree  would  remain,  hence  the  practice 
is  to  remove  only  such  limbs  as  show  evidence  of  decline. 

2.  Open  up  the  tree.  If  the  tree  has  become  too  thick 
and  ''bushy,"  it  will  be  necessary  to  remove  a  portion  of 
the  limbs  or  a  weakening  of  the  fruit-spurs  will  result  and 
fruit  inferior  in  size,  color,  and  quality  will  be  produced. 
Rubbing  limbs  should  be  cut  off,  and  long  rangy  ones  that 
are  out  of  proportion  should  be  headed-back. 

3.  Avoid  the  removal  of  fruit-spurs.  This  is  paramount, 
and  a  thorough  understanding  of  the  way  a  tree  bears  its 
fruit  must  be  one  of  the  basic  guides  in  the  removal  of 
branches.  There  are  times  when  it  is  desirable  to  remove 
some  of  the  spurs,  or  portions  of  the  individual  spur,  in  order 
to  improve  those  that  remain. 

4.  Stubs  are  to  be  avoided.  In  removing  limbs  or 
branches,  no  matter  how  small,  they  should  be  cut  close  to 
the  trunk  or  adjoining  branch  to  which  they  are  attached. 
This  is  not  so  important  with  the  peach  as  with  the  apple, 
owing  to  the  strong  growth  of  the  former  which  will  more 
quickly  envelope  a  small  stub. 


98  POMOLOGY 

5.  As  a  rule,  it  is  desirable  to  remove  the  "suckers"  or 
"water-sprouts "  that  may  arise  throughout  the  tree.  Strong 
sucker  growth  along  the  main  limb  may  be  an  evidence  of 
decline  in  the  branch  and  the  outer  extremities  may  be 
robbed  of  vitality  if  they  are  allowed  to  develop.  On  the 
other  hand,  it  is  often  desirable  to  retain  a  portion  for  re- 
placing limbs.  In  such  a  case,  it  is  usually  desirable  to  head 
them  back  and  treat  in  about  the  same  way  as  a  young  tree. 

85.  Renovation  pruning. — The  dehorning  of  apple  trees 
or  the  cutting  back  of  one-third,  one-half  or  even  more  of 
the  tops  of  old  trees,  leaving  naked  branches  from  which  to 
grow  a  new  top,  has  had  its  advocates.  This  procedure  re- 
quires great  caution,  for  it  is  not  unconmion  to  find  that  trees 
subnormal  in  vitality  may  have  their  death  hastened  by 
such  a  practice,  although  for  the  first  two  or  three  years  the 
operation  appears  successful.  It  is  usually  better  to  cut 
back  a  portion  of  the  tree  at  a  time  and  always  cut  to  a  side 
branch  rather  than  trust  to  the  outgrowth  of  "suckers" 
or  water-sprouts.  Such  trees  should  be  stimulated  by  til- 
lage or  the  application  of  manures  or  fertilizers  as  a  safe- 
guard against  injury.  The  peach,  on  the  other  hand, 
may  be  headed-back  severely  with  comparative  impunity. 
Branches  may  often  be  developed  in  desirable  places  on  an 
old  tree  by  making  use  of  water-sprouts  which  arise  in  those 
places.  These  sprouts  may  come  into  bearing  in  about  three 
years  and  are  handled  in  pruning  in  much  the  same  way  as  a 
young  tree. 

86.  Summer  pruning. — As  dormant  pruning  has  been 
widely  advocated  to  induce  vigorous  wood  growth,  so  sum- 
mer pruning  has  been  recommended  to  encourage  fruit- 
fulness.  The  practice  is  an  old  one  and  has  commonly  been 
credited  as  a  means  of  bringing  tardy  bearers  into  fruiting. 
There  is  veiy  little  experimental  evidence  on  which  to  base 
this   teaching,  but  it  is  well    entrenched  in  the  literature. 


PRUNING  99 

The  value  of  the  practice  seems  to  depend  on  the  variety, 
soil,  climate,  time,  and  particularly  the  type  of  pruning  (of 
which  there  are  veiy  many),  and  doubtless  on  the  internal 
condition  of  the  tree.  It  is  true  that  summer  pruning  will 
often  decrease  vegetative  growth,  but  it  does  not  necessarily 
follow  that  fruitfulness  accompanies  such  enfeebled  growth. 
Some  experiments  have  been  conducted  to  detennine  the 
value  of  this  practice,  but  it  scarcely  seems  possible  as  yet 
to  hannonize  the  views  held  by  different  investigators  on 
its  value,  but  certainly  it  is  pernicious  at  times.  Doubtless 
the  difficulty  is  due  to  the  different  methods  employed  and  to 
the  vaiying  influence  exerted  on  the  materials  manufac- 
tured and  stored.  Some  have  practiced  both  a  thinning- 
out  and  heading-back  of  the  branches  relatively  early  or 
late  in  any  given  season,  while  others  have  merely  pinched 
the  tips  of  the  branches.  The  results  must,  therefore,  vary 
accordingly. 

For  eastern  conditions  the  consensus  of  opinion  seems 
to  be  that  summer  pruning  is  not  a  desirable  practice,  as 
the  trees  are  enfeebled  and  the  effects  on  bearing  are  doubt- 
ful, often  negative,  and  frequently  the  yield  is  decreased. 
In  England  where  dwarf  trees  are  rather  widely  grown, 
there  is  some  difference  of  opinion  on  its  value,  ^  but  the 
growers  are  more  favorable  to  summer  pinching  if  any 
treatment  is  to  be  given.  However,  Bedford  and  Picker- 
ing -  report  after  ten  years'  work  that  "Summer  pruning, 
shaping,  or  pinching,  seem  to  have  been  followed  by  no  good 
results  in  the  case  of  our  trees,  rather  the  reverse;  and  we 
should  not,  therefore,  recommend  such  treatment." 

Dickens  ^  reports  a  successful  use  of  summer  pruning 

1  Gardener's  Chronicle.       3d  Series,  Vol.  41,  pp.  400-40.3;  406-407. 
1907.    Jour.  Royal  Hort.  Soc,  Vol.  33,  Part  2,  pp.  487-499.    1908. 
^Woburn  Expt.   Fruit  Farm,   5th  Rcpt.   1905. 
» Dickens,  A.     Kans.  Agr.  Exp.  Sta.  Bull.  136.    1906. 


100  POMOLOGY 

with  ten-year-old  apple  trees  that  had  not  previously  fruited. 
The  extent  of  the  results  reported,  however,  are  scarcely 
sufficient  to  justify  the  practice. 

Batchelor  and  Goodspeed  ^  conducted  pruning  inves- 
tigations with  the  Jonathan  and  Gano  apples.  The  trees 
were  five  j^ears  old  when  the  work  started  and  it  was  con- 
tinued for  four  years.  The  winter-pruned  trees  averaged 
1055  pounds  to  a  tree  for  the  four  years  as  compared  with 
937  pounds  from  the  summer-pruned  trees,  or  a  loss  for  the 
period  of  257  boxes  to  the  acre.  Thus  the  summer  pruning 
resulted  in  less  fruit  rather  than  more  in  this  experiment, 
but  whether  the  reduction  is  due  to  a  lessened  area  of  fruit- 
bearing  wood  removed  by  the  sununer  pruning,  or  to  an 
actual  depression  of  fruit-bud  formation  is  not  clear. 

Drinkard,-  working  with  dwarf  apple  trees,  found  that: 
"Summer  pruning  of  branches  of  the  tree  the  latter  part  of 
June,  when  fruit-buds  normally  begin  to  show  differentia- 
tion, checked  wood  growth  the  year  in  which  the  pruning 
was  done,  and  greatly  stimulated  the  formation  of  fruit- 
buds,  as  was  shown  by  the  bloom  and  crop  of  fruit  the  fol- 
lowing year."  The  foliage  of  these  trees  was  reduced  50  per 
cent  by  the  pruning  and  as  a  result  the  "trees  made  very 
short  growth  in  annual  shoots." 

Summer  pruning  has  been  advocated  by  Lewis  for  west- 
ern conditions,  for  young  trees  of  non-bearing  age  in  order 
to  produce  a  development  of  laterals  and  to  gain  practically 
one  season  by  the  operation.^  The  pinching  or  pruning 
should  be  done  rather  early  in  the  season,  or  as  soon  as  the 
rampant  growth  can  be  observed,  which  will  be  about  the  mid- 
dle of  June  under  Oregon  conditions.     The  pruning  would 

1  Batchelor,  L.  D.,  and  W.  E.  Goodspeed.  Utah  Agr.  Exp.  Sta.  Bull. 
140.    1915. 

2  Drinkard,  A.  W.  Jr.      Va.  Agr.  Exp.  Sta.  Tech.  Bull.  5.    1915. 

3  Ore.  Agr.  Exp.  Sta.  Bull.  130.     1915. 


PRUNING  101 

be  much  the  same  as  for  the  following  sprhig,  althougli  the 
trees  may  also  need  some  thinning-out  again  and  perhaps 
some  cutting  back  the  following  season  at  the  time  of  dor- 
mant pruning.  The  object  of  summer  pruning  for  these 
young  trees  is  to  balance  up  the  tree  and  to  avoid  heavy  dor- 
mant pruning  rather  than  to  induce  fruitfulness.  Trees  just 
reaching  bearing  age  (four  to  seven  years)  are  sometimes 
sunnner-pruned  to  induce  fruitfulness  and  hence  the  time 
for  the  operation  is  later  in  the  season,  about  the  middle  of 
July,  or  when  the  terminal  bud  begins  to  form.  The  cutting 
is  again  made  where  it  is  desired  to  force  out  new  laterals 
and  has  a  tendency  on  some  varieties  to  bring  about  fruiting 
the  following  season.  When  this  work  is  done  properly,  it 
is  claimed  that  veiy  little  secondaiy  growth  will  take  place 
and  practically  no  devitalizing  effect  will  result  to  the  trees, 
as  is  often  the  case  under  the  conditions  of  the  East. 

Vincent  ^  reports  that  in  a  four  years '  experiment  in  Idaho 
with  summer  pruning,  the  results  are  not  entirely  consist- 
ent. With  Wagener  the  increase  in  yield  amounted  to  HI 
per  cent,  with  the  Grimes  52.8,  Jonathan  2.4,  and  Rome  1.6 
per  cent.  The  color  of  the  fruit  from  the  summer-pruned 
trees  was  superior. 

1  Vincent,  C.  C.    Idaho  Agr.  Exp.  Sta.  Bull.  84.     1915. 


CHAPTER  VI 

THE  THINNING  OF  FRUIT 

Thinning  of  fruit  is  an  established  orchard  practice  at  the 
present  time.  It  has  long  since  passed  the  experimental 
stage.  However,  many  successful  commercial  growers  do 
not  include  it  among  their  operations  because  its  necessity 
has  not  been  so  apparent  as  has  that  of  pruning  or  spraying. 
The  western  growers  have  been  pioneers  in  this  work  from  a 
commercial  standpoint  probably  because  their  practice  of 
packing  fruit  in  small  packages,  notably  the  standard  box, 
has  made  thinning  not  only  necessary  but  profitable.  The 
present  tendency  is  for  all  fruit-producing  states  to  have  a 
packing  and  grading  law,  and  when  this  is  accomplished  the 
thinning  of  fruit  will  doubtless  become  still  more  general. 

87.  Definition. — By  thinning  is  meant  the  removal  of 
a  portion  of  the  crop  of  fruit  from  the  trees  shortly  after 
the  June  drop  (/.  e.,  soon  after  it  has  set)  to  prevent  over- 
bearing. 

88.  History  of  thinning. — The  practice  of  thinning  fruit 
is  by  no  means  modern,  but  like  many  other  agricultural 
operations,  no  definite  time  or  place  seems  recorded  as  its 
origin.  The  pomological  writers  for  many  years  have  men- 
tioned it  as  desirable  and  have  urged  its  use.  In  his  "Trea- 
tise of  Fruit  Trees"  published  in  London  (1768),  Thomas 
Hitt  says,  "When  there  is  too  great  a  quantity  of  fruit 
suffered  to  remain  upon  any  part  of  a  tree,  it  is  not  so  good 
as  if  there  were  only  a  proper  quantity  left  on;  and  some- 
times a  tree  becomes  weak  by  bearing  too  plentifully.  .  .  . 

"Fruits  are  thinned  the  best  either  with  a  very  narrow- 
102 


THE  THINNING  OF  FRUIT  103 

pointed  penknife  or  scissors ;  for  by  nipping  them  off  with  the 
thumb  and  forefinger,  those  designed  to  be  left  on  are  often 
displaced,  as  also  the  young  branches  and  leaves  .... 

"Though  I  advise  to  thin  fruit  at  different  times,  yet  it 
should  not  be  done  later  than  the  month  of  May;  for  if  they 
are  suffered  to  grow  pretty  large  they  rob  one  another,  and 
none  should  be  left  on  so  near  together  as  to  touch  before 
they  be  full  grown;  for  they  are  apt  to  throw  each  other  off 
or  at  least  to  spoil  their  shapes.  Besides,  they  never  come 
to  the  size  they  would  otherwise  do,  and  large  fruit  when 
ripe  is  always  the  best  flavored.  ..." 

Many  of  the  same  ideas  have  been  repeated  in  subsequent 
works  on  fruit-culture,  some  writers  enlarging  and  elaborating 
on  these  views.  Two  or  three  points  are  practically  always 
mentioned  by  the  early  as  well  as  modern  writers,  such  as: 
the  value  of  the  practice  to  increase  the  size  and  appearance 
of  the  fruit;  as  a  means  of  bringing  about  annual  bearing; 
and  to  prevent  the  breaking  of  trees  from  overbearing. 

89.  Philosophy  of  thinning. — The  theory  of  thinning  is 
very  simple,  a  theory  that  is  paralleled  in  many  branches  of 
agriculture.  The  farmer  thins  his  corn,  the  gardener  his 
carrots  and  beets,  the  florist  disbuds  his  carnations,  chrysan- 
themums, and  many  other  plants,  and  the  forester  thins  his 
stand  of  timber,  all  for  the  same  general  purpose  of  allowing 
the  remaining  plants  or  parts  ample  room  and  food  for 
development,  or  in  other  words  to  relieve  the  struggle  for 
existence.  For  the  same  reason  the  fruit-grower  also  removes 
a  portion  of  his  fruit  when  it  sets  too  heavily. 

It  is  natural  for  every  plant  to  reproduce  itself,  for  two 
of  the  fundamental  laws  in  plant  and  animal  life  are  nutri- 
tion and  reproduction.  Fruit-trees,  however,  very  often  set 
a  great  many  more  fruits  than  the}^  can  properly  mature. 
This  distributes  the  moisture  and  food  materials  in  so  many 
channels  that  it  results  in  small  and  inferior  fruit.    In  this 


104 


POMOLOGY 


connection  must  be  considered  the  characteristics  of  certain 
varieties,  for  it  is  well  known  that  some  heavy  bearers  are 
not  apparently  injured  by  their  large  crops,  and  conversely 
some  light  bearers  never  so  utilize  their  energies  as  to  produce 
heavy  yields. 

90.  Fruit  production  exhaustive.^ — It  is  an  exhaustive 
process  for  plants  to  produce  pollen  and  seeds.  The  more 
the  tree  can  be  relieved  of  seed  production  and  not  sacrifice 
the  crop,  the  more  it  is  helped  to  balance  up  its  life  processes, 
namely:  wood  growth,  crop  production,  fruit-  and  leaf-bud 
formation,  and  the  laying  up  of  reserve  materials.  Green  ^ 
has  shown  that  asparagus  plants  which  fruit  do  not  produce 
as  large  'Hips"  for  cutting  in  the  spring  as  those  that  are 
barren.  While  this  is  not  entirely  relevant,  it  illustrates 
the  principle  involved : 

Table  XVII 


ASPARAGUS.- 


-product  from  fifty  plants  each,  male  and  female 
(after  green) 


Product  from 

fifty 

male  plants 

Product  from 

fifty 

female  plants 

First  period   10  days 

ounces 

37 

104 

266 

203 

ounces 
21 

Second  period,  10  days 

68 
164 

154 

610 

407 

"This  shows  a  gain  of  the  male  over  the  female  plants 
of  seventy-six  per  cent  for  the  first  period  and  a  fraction 
less  than  fifty  per  cent  for  the  whole  season. " 

1  Green,  W.  J.  Bull.  Ohio  Agr.  Exp.  Sta.  Vol.  Ill,  No.  9,  1890, 
p.  242. 


THE  THINNING  OF  FRUIT  105 

Green  ^  also  suggests  that  the  varieties  of  imperfect 
flowering  strawberries  are  more  productive  than  the  perfect 
flowering  sorts  because  of  the  latter's  exhaustion  in  pollen 
production.  Later-  the  Ohio  Station  reported  as  follows: 
"The  average  yield  from  each  eighteen  foot  row  of  perfect 
varieties  (139  varieties)  was  5.47  quarts,  and  from  each 
row  of  the  same  length  of  imperfect  varieties  (66  varieties) 
was  7.19  quarts.  There  are  some  high-yielding  perfect 
flowered  varieties,  and  some  among  the  imperfect  that 
give  low  yields;  but  it  is  generally  recognized  as  a  fact  that 
the  former,  as  a  class,  are  less  proHfic  than  the  latter." 
Fletcher,^  however,  states  that  while  this  probably  is 
correct  if  applied  to  a  grand  average  of  all  pistillate  and 
staminate  varieties,  it  is  not  true  when  individual  varieties 
are  considered.  "For  all  practical  purposes  staminate  and 
pistillate  varieties  arc  equally  prolific."  So  this  evidence 
from  other  plants  would  seem  to  add  weight  to  the  theory 
that  fruit  production  is  an  exhaustive  process  in  the  economy 
of  the  plant. 

91.  Dependence  of  fruit  on  foliage  immediately  surround- 
ing it. — The  amount  of  elaborated  food  manufactured  liy 
the  tree  is  governed  by  the  area  of  healthy  foliage  that  it 
possesses.  And,  furtheraiore,  each  fruit  depends  largely 
on  the  leaves  in  rather  close  proximity  to  it.  Therefore, 
because  only  one  side  of  the  tree  or  one  branch  is  heavily 
loaded,  it  does  not  obviate  the  need  of  thinning  that  part. 

92.  Objects  of  thinning. — The  objects  of  thinning  fruit 
may  be  summarized  as  follows : 

1.  To  increase  the  size,  color,  quality,  and  uniformity  of 
the  fruit. 

1  Green,  W.  J.  Bull.  Ohio  Agr.  Exp.  Sta.,  Vol.  Ill,  No.  7,  1890, 
p.  221. 

2/6id.,  Bull.  236(1912). 

3  Fletcher,  S.  W.    Strawberry-Growing,    p.  130.    New  York,  1917. 


106  POMOLOGY 

2.  To  prevent  the  breaking  of  the  limbs. 

3.  To  reduce  disease  and  insect  injury  to  the  fruit. 

4.  To  maintain  the  vigor  of  the  trees. 

5.  To  secure  more  regular  bearing. 

6.  To  decrease  the  labor  of  handling  the  crop. 

93.  To  increase  the  size  of  the  fruit. — Probably  the 
greatest  advantage  of  thinning  is  the  increase  in  the  size  of 
the  remaining  fruits  and  this  is  well  borne  out  by  experi- 
mental evidence.  In  fact,  practically  all  data  are  expressed 
in  terms  of  percentage  of  large  and  small  fruits  from  the 
thinned  and  unthinned  trees,  and  the  amount  of  each.  It 
is  true,  of  course,  that  the  increase  in  size  will  depend  on 
several  factors,  especially  the  amount  of  fruit  which  has  set. 
It  is  seldom  that  a  heavily  laden  tree  will  not  show  a  marked 
increase  in  size  of  fruit,  if  it  is  thinned  sufficiently  early  and 
enough  is  removed.  Disappointment  is  likely  to  result  if  a 
grower  has  his  first  experience  in  thinning  a  tree  that  is 
carrying  but  a  moderate  crop.  The  age  and  vigor  of  the 
trees  are  also  important  factors  determining  the  amount  of 
fruit  an  individual  tree  can  carry  through  to  maturity. 
The  varietal  factor  again  plays  an  important  part,  as  does 
the  cultural  treatment.  The  following  tables  are  fairly 
representative  of  the  influence  of  thinning  apples  on  the 
size  of  the  remaining  fruit: 


THE  THINNING  OF  FRUIT 


107 


Table  XVIII 

THINNING   APPLES 

All  imperfect  fruits  were  removed  and  all  others  thinned  to  not 
than  four  inches  apart.     Yield  to  a  tree  for  three  years 
(after  beach) 


Treatment 

Barrel  fruit 

No.  1 

No.  2 

Total 

Baldwin 

Thinned. . 

Bu. 

39  2 

Per  cent 

75 . 5 
()0.9 

80.8 
79.4 

Bu. 

12.7 
24.1 

7.2 
7.3 

Per  cent 

24.5 
39.1 

19.2 
20.0 

Bu. 
51  9 

Unthinned 

Greening 

Thinned 

37.5 

30.2 
28.1 

01.6 
37  4 

Unthinned 

35.4 

Table  XIX 


THINNING  apples  IN  AN  OHIO  ORCHARD. 

(after  ballou) 


ROME  BEAUTY 


Tree  No.  1.  Unthinned.    Number  of  apples  set  and  matured 
on  tree  4376 


No.  of 
apples 
picked 

Weight, 
pounds 

Bushels 

Per- 
centage 
of  grade 

Firsts                

1750 
1950 
670 

488 
390 
134 

9.76 

7.8 

2.68 

48  22 

Seconds 

Defective  and  small 

38.53 
13.24 

4376 

1012 

20.24 

108 


POMOLOGY 


Table  XIX — Continued 

ROME    BEAUTY 


Tree  No.  2.  Thinned  to  8  inches   apart.     Number  of  apples  set  4178; 
number  taken  off,  771 


No.  of 
apples 
picked 

Weight, 
pounds 

Bushels 

Per- 
centage 
of  grade 

Firsts 

2656 
445 
306 

3407 

830 
99 
68 

16.6 
1.98 
1.36 

S3  24 

Seconds 

Defective  and  small 

9.92 
6.82 

997 

19.94 

Table  XX 


thinning  apples  in  a  new  hampshire  orchard.    baldwin 
(after  gourley) 


Original 
number 
of  apples 

After 
thinning 

Per  cent 
No.l 

Per  cent 
No.  2 

Per  cent 
culls 

1.  Unthinned  tree.  .  .  . 

2.  Thinned  tree 

3.  Thinned  tree 

4.  Thinned  tree 

5.  Thinned  tree 

6.  Unthinned  tree .... 
Average  for  unthinned 

4055 
3453 
3350 
3130 
3895 
2938 

2415 
2061 
1760 

2277 

16 

58 
82 
79 
71 
48 

32 

72 

78 
•     40 
16 
19 
26 
43 

60 

25 

4 
1 
.6 

1 
1 

7 

5 

Average    for    thinned 
trees 

—1 

Auchter  -  says,  "In  thinning  bearing  Ben  Davis  trees  in 
1914  it  was  found  that  the  apples  on  the  unthinned  trees  were 
2  Auchter,  E.  C.    W.  Va.  Agr.  Exp.  Sta.  Bull.  162.     1917. 


THE  THINNING  OF  FRUIT  109 

so  small  that  65.7  per  cent  of  the  crop  was  less  than  23^ 
inches  in  diameter,  34.1  per  cent  of  the  crop  was  between 
2}4:  and  2^  inches  and  practically  none  was  above  2^ 
inches.  In  contrast  to  this,  the  crop  from  those  trees  thinned 
six  to  seven  inches  apart  had  only  13.6  per  cent  of  the  fruit 
less  than  23<4  inches,  while  71.6  per  cent  was  between  23-i 
and  2%  inches,  and  14.6  per  cent  was  more  than  2%  inches. 
Although  there  were  nearly  2000  more  apples  per  tree  on 
the  unthinned  trees  at  picking  time,  still  due  to  their  small 
size,  they  produced  less  than  one-half  as  great  a  total  market- 
able quantity." 

The  following  average  results  of  several  experiments  on 
thinning  apples  are  tabulated  and  may  be  considered  as 
fairly  representative  of  the  increase  in  size  from  thinning: 

10  experiments,  100  trees. 

8  varieties,  Baldwin,  Greening,  Stark,  Ben  Davis,  Rambo, 
Rome,  Winesap,  Jonathan. 

5  states.  Nova  Scotia,  New  Hampshire,  New  York,  Ohio, 
Colorado. 

Table  XXI 


EFFECT  OF  THINNING 

ON  SIZE  OF  FRUIT 

Per  cent  No.  1 

Per  cent  No.  2 

Per  cent  Culls 

Unthinned     Thinned 
43                  71 

Unthinned 
45 

Thinned 
23 

Unthinned 
6 

Thinned 
3 

94.  Thinning  to  improve  color. — ^An  increase  in  color  is 
one  of  the  usual  results  of  thinning.  In  most  experiments  the 
color  of  the  fruits  (especially  on  peaches  and  apples)  has  been 
increased,  although  it  must  be  seen  to  be  appreciated.  In 
an  unpubHshed  experiment  conducted  by  the  author  with 
Grimes  Golden  apples,  the  size  was  not  so  materially  affected 
as  was  the  color.  Practically  every  apple  was  a  fancy 
"box"  grade,  having  developed  a  rich  golden  color  and  a 


110  POMOLOGY 

pink  blush  on  one  cheek,  as  compared  with  the  check  trees 
on  which  nearly  all  the  fruit  was  a  little  undersized,  of  a 
greenish  color,  and  had  no  evidence  of  the  pink  check. 

95.  Quality  improved  by  thinning. — Quality  is  more 
difficult  to  define  and  tabulate,  but  the  unanimous  report  of 
experimenters  and  orchardists  is  that  the  enlarged  and 
highly  colored  fruit  is  better  in  quality  than  the  smaller  and 
poorer  specimens. 

96.  Thinning  to  prevent  breaking  of  limbs. — No  one  who 
has  been  observing  orchards  for  a  period  of  years  has  failed  to 
notice  the  appalling  breaking  of  limbs  as  a  result  of  over- 
bearing. Some  trees  and  even  orchards  are  so  ruined  after 
some  exceptionally  heavy  crop  that  they  never  regain  in  form 
and  symmetry  what  they  lose  in  one  season  from  lack  of 
proper  pruning  and  thinning.  The  use  of  props  is  also  much 
reduced  or  entirely  obviated  in  an  orchard  that  has  been  well 
thinned. 

97.  Thinning  to  reduce  disease  and  insect  injury. — 
In  thinning  the  fruit,  any  that  have  been  injured  by  insect 
stings  or  early  attacks  of  fungus,  as  well  as  ill  shaped  speci- 
mens, would  be  removed.  In  the  case  of  peaches  and  plums, 
the  amount  of  such  disease  as  brown-rot  is  much  reduced 
when  the  fruit  does  not  hang  so  close  together  and  also  the 
spray  solutions  can  better  cover  the  entire  surface  of  each 
specimen.  In  the  case  of  the  apple,  there  would  be  less 
opportunity  for  the  second  brood  codhn-moth  to  find  an 
entrance  if  no  two  fruits  touch.  Thus  the  instances  might 
1)6  multiplied  of  greater  injury  from  insect  and  disease  if  the 
fruit  is  not  thinned. 

98.  Thinning  to  maintain  the  vigor  of  the  trees. — It  is 
difficult  to  present  experimental  evidence  directly  on  this 
problem,  but  it  has  been  the  experience  and  observation  of 
fruit-growers  for  many  years  that  a  tree  (especially  a  young 
one)  which  bears  an  excessive  crop  of  fruit  may  be  perma- 


THE  THINNING  OF  FRUIT  111 

nently  injured  as  a  result  or  may  at  least  require  several 
years  again  to  bear  fruit  in  quantity.  This  difficulty  may  be 
obviated  by  nature  through  a  lack  of  setting  of  the  blossoms 
and  indeed  this  is  connnon,  notably  with  peach  trees  just 
reaching  the  bearing  age.  However,  when  a  natural  abscis- 
sion does  not  take  place,  it  is  desirable  to  thin  the  fruit. 

It  would  probably  be  difficult  to  cite  a  season  when  the 
above  principle  was  so  evident  as  after  the  winter  of  1917- 
18.  Winter-injury  was  common  throughout  the  northern 
poi-tions  of  the  country  and  the  testimony  of  a  vast  number 
of  growers  was  that  the  trees  that  bore  heavily  in  1917 
suffered  the  greatest  injury  from  the  following  winter  and 
many  were  killed  outright.  Hence  not  only  young  but  also 
mature  trees  may  have  their  vigor  maintained  by  judicious 
and  sj^stematic  thinning. 

99.  Thinning  to  secure  more  regular  bearing  applies 
more  particularly  to  the  poach  than  to  the  other  tree-fruits. 
In  experiments  with  mature  apple  trees,  the  results  have 
usually  been  negative.  This  is  explained  on  the  grounds  that 
the  fruit-ljuds  have  started  to  differentiate  as  such  before  the 
thinning  and  hence  it  can  have  no  effect.  Writers  have, 
however,  often  urged  that  annual  bearing  was  one  of  the 
greatest  advantages  to  l)e  gained  by  thinning.  This  seems 
most  reasonable,  and  the  teachings  of  plant  physiology 
woukl  give  it  some  support.  Just  why  the  peach  should  be  so 
responsive  in  this  direction  and  the  apple  be  unaffected  is  not 
clear  unless  it  is  due  to  a  longer  period  of  fruit-bud  formation 
and  type  of  bearing. 

Walker  reports  as  follows  in  regard  to  the  peach:  ^  ''The 
trees  on  which  the  first  lot  (which  had  been  thinned)  grew 
had  a  strong  set  of  fruit  buds  for  the  next  season's  crop;  the 
trees  on  which  the  second  lot  (unthinned)  grew  were  scarcely 
able  to  live." 

1  Walker,  E.    Ark.  Agr.  Exp.  Sta.  Bull.  79.    1903. 


112  POMOLOGY 

The  same  observation  is  made  by  Gould  ^  who  says:  "The 
effect  on  the  tree  (peach)  of  wise  thinning  extends  far  beyond 
the  current  crop,  for  it  is  a  mortgage  on  future  crops  if  the 
tree  is  seriously  depleted  by  overbearing." 

With  the  apple,  however,  the  evidence  is  not  satisfactory 
and  usually  the  statements  are  general  and  without  sufficient 
experimental  evidence.  It  is  possible  that  thinning  younger 
trees  may  promote  annual  bearing,  but  there  is  no  satisfac- 
tory evidence  to  present  on  this  point.  It  is  probable  that 
growers  may  be  inclined  to  credit  one  practice  with  the 
results  obtained  when  several  factors  are  involved,  and  thus 
'prejudiced  statements  arise. 

Downing's  writings  ranked  high  in  the  pomological  litera- 
ture of  a  half  a  century  ago,  and  his  statement  may  be  cited 
as  fairly  typical  of  others.  "When  half  the  fruit  is  thinned 
out  in  a  young  state,  leaving  only  a  moderate  crop,  the  apple, 
like  other  fruit  trees,  will  bear  every  year,  as  it  will  also  if  the 
soil  is  kept  in  high  condition.  The  bearing  year  of  an  apple 
tree,  or  a  whole  orchard,  may  be  changed  by  picking  off  the 
fruit  when  the  trees  show  good  crops,  allowing  it  to  remain 
only  in  the  alternate  seasons  which  we  wish  to  make  the 
bearing  year."  - 

Against  this  statement  of  Downing  the  work  of  Beach  ^ 
must  be  considered,  in  which  after  four  years'  investigation 
he  says,  "It  will  not,  on  mature,  well  established  trees, 
materially  influence  the  regularity  of  production  or  the 
amount  of  fruit  setting  for  subsequent  crops.  The  profit,  if 
there  be  any,  must  come  from  the  crop  thinned."  Also, 
Auchter  ^  after  five  years'  work  on  this  subject,  "while  final 

1  Gould,  H.  P.  Peach-Growing,  p.  299,  New  York,  1918.  Rural 
Science  Series. 

2  Downing,  A.  J.    Fruits  and  Fruit  Trees  of  America,  p.  63.    1900. 
^  Beach,  S.  A.    Loco   cit. 

*  Auchter,  E.  C.    Loco  cit. 


THE  THINNING  OF  FRUIT  113 

conclusions  are  not  attempted,  results  indicate  that  thinning 
does  not  influence  subsequent  crops  nor  cause  trees,  naturally 
biennial  in  bearing  habit,  to  bear  a  crop  each  year."  The 
author  also  has  reported  that  "Trees  which  were  thinned  to 
twelve  inches  apart  produced  no  more  blossoms  the  following 
spring  than  did  the  unthinned  trees  which  had  borne  an 
excessive  crop."  ^ 

100.  Thinning  to  decrease  the  labor  of  handling  exces- 
sive crops  of  small  fruit  is  of  considerable  consequence  from 
a  commercial  standpoint.  The  work  of  picking  and  handling 
a  crop  in  which  a  considerable  proportion  of  the  fruit  is  small 
or  below  a  standard  merchantable  grade  is  not  economical. 
That  this  labor  can  be  appreciably  reduced  is  established  in 
the  foregoing  paragraj^hs. 

101.  The  effect  of  thinning  on  the  total  crop. — As  in- 
dicated by  data  previously  cited,  not  infrequently  the  total 
crop  from  a  tree  from  which  half  the  fruit  has  been  removed 
will  be  as  great  as  from  an  unthinned  tree  carrying  practically 
the  same  amount  of  fruit  as  was  originally  on  the  thinned 
one.  This  of  course  is  possible  because  of  the  increased  size  of 
the  remaining  fruit.  Often  the  crop  is  reduced  in  total  yield 
and  in  some  cases  it  results  in  actual  loss.  Perhaps  the 
experience  of  the  workman  is  the  only  safeguard  in  deter- 
mining how  much  fruit  should  be  removed,  and  even  he  will 
err  in  judgment  at  times. 

Excerpts  from  experiments  conducted  in  several  states 
show  the  range  of  variation  in  this  regard  and  fairly  repre- 
sent the  situation.  It  is  presumed  that  the  trees  in  any  given 
experiment  are  similar  in  size  and  amount  of  total  fruit 
originally  set. 

1  Gourley,  J.  H.    N.  H.  Agr.  Exp.  Sta.  Tech.  BuU.  9.     1915. 


114  POMOLOGY 

Table  XXII 

RELATION  OF  THINNING  VERSUS  NON-THINNING  TO  THE  TOTAL  CROP 

Average  a  tree,  lbs. 

Colo.        Unthinned     2  trees 843 

Thinned        8  trees 610 

Utah        Unthinned     4  trees 254 

Thinned         4  trees 269 

Ohio         Unthinned     6  trees 924 

Thinned         9  trees 954 

W.  Va.     Unthinned     3  trees  (young) 159 

Thinned       10  trees  (young) 116 

Unthinned     1  tree 664 

Thinned         1  tree 648 

Unthinned     1  tree 670 

Thinned         1  tree 468 

Unthinned     1  tree 534 

Thinned         1  tree 528 

Average  unthinned  trees 578  lbs. 

Average  thinned  trees 513    " 

The  average  difference  in  these  particular  experiments 
is  65  pounds  or  about  13^  bushels  to  a  tree  in  favor  of  the 
unthinned  tree.  While  no  set  of  figures  could  be  accepted  as 
representing  the  exact  relation  of  thinning  to  the  total  crop, 
as  no  two  experiments  would  be  alike  since  so  many  factors 
are  involved,  yet  they  are  indicative  of  what  might  be  ex- 
pected. Although  these  figures  show  that  the  total  crop  may 
be  somewhat  reduced,  they  must  be  viewed  in  the  light  of  the 
discussion  under  size  of  fruit  and  it  must  be  realized  that  the 
economic  value  of  the  crop  is  very  likely  to  be  higher  from  the 
thinned  trees. 

102.  When  to  thin. — The  time  for  thinning  will  vary 
with  the  variety,  season,  latitude,  and  possibly  other  factors. 


THE  THINNING  OF  FRUIT  115 

As  a  rule,  the  sooner  the  thinning  is  done  after  the  June  drop, 
the  better  will  be  the  results.  The  apples  will  be  nearly  an 
inch  in  diameter  at  that  time,  some  varieties  larger  and  some 
smaller.  This  will  be  the  middle  of  June  with  peaches  and 
plums,  and  the  last  of  June  to  the  middle  of  July  (depending 
on  the  locality),  with  apples  and  pears.  When  the  season  is 
late,  it  is  advisable  to  begin  the  work  before  the  June  drop  is 
quite  over  or  it  will  be  delayed  until  late  in  July  in  the 
northern  latitudes.  When  the  work  is  left  until  late  in  the 
season,  the  beneficial  results  are  often  reduced.  The  reasons 
for  thinning  about  the  time  of  June  drop  are : 

1.  The  size  will  be  increased  to  a  greater  extent. 

2.  The  development  of  seeds  and  "  pits"  drains  the  energies 

of  the  tree. 

3.  If  done  before  that  time,  it  is  probable  that  many 

fruits  which  were  thinned  would  not  have  set,  thus 
wasting  labor  and  causing  too  great  a  distance  be- 
tween fruits  after  the  natural  abscission  has  taken 
place. 
It  is  the  experience  of  most  growers  that  if  thinning  is 
delayed  until  late  in  the  season,  the  size  of  fruit  is  not  per- 
ceptibly increased.    The  author  has  seen  distinct  evidences  of 
this  on  several  occasions,  especially  with  the  apple. 

In  order  to  establish  that  early  thinning  lessens  the  drain 
on  the  resources  of  the  tree,  a  chemical  analysis  of  the  seeds 
and  pits  early  in  the  season  and  later  must  be  considered. 

As  already  referred  to  in  Chapter  I,  Bigelow  and  Gore  ^ 
report  on  the  composition  of  the  Triumph,  Rivers,  Early 
Crawford,  Elberta,  Heath,  and  Smock  varieties  of  the 
peach,  at  three  periods  in  the  development  of  the  fruit. 
First,  immediately  after  the  time  of  the  June  drop;  second, 
when  the  stone  had  hardened;  and  third,  when  the  fruit  was 

•  Bigelow,  W.  D.,  and  H.  C,  Gore.  U.  S.  Dept.  Agr.  Bur.  Chem.  Bull. 
97.     1905. 


116 


POMOLOGY 


ripe  for  picking.    The  average  composition  of  these  varieties 
is  shown  in  the  following  table : 


Table  XXIII 

AVERAGE    COMPOSITION    OF    SIX    VARIETIES    OF    PEACHES    AT    DIFFERENT 
STAGES    OF    GROWTH    (AFTER    BIGELOW    AND    GORE) 


State  of  growth 

Weight  of 

Total  solids  in 

Peach 

Flesh 

Stone 

Kernel 

Flesh 

Stone 

Kernel 

June  drop 

Stone  hardened.  . 
Market  ripe 

Grams 

9.51 

16.75 

73.59 

% 
64.55 
71.54 
92.49 

% 

32.50 

25.82 

6.86 

% 
2.94 
2.89 
0.65 

7o 
14.77 
16.97 
14.04 

% 

9.37 
27.35 
66.94 

% 

6.89 

7.54 

44.78 

Gould's  ^  comments  on  this  table  interpret  the  problem 
in  its  relation  to  earl}^  thinning:  "The  most  important  feature 
of  this  table  from  the  standpoint  of  thinning  is  in  showing  the 
rapid  rate  of  increase  of  the  solids  in  the  stones  while  passing 
from  the  June  drop  stage  to  the  hardening  stage.  The  first 
analyses  of  the  stone-hardened  stage  were  made  June  23  and 
28,  depending  on  the  variety.  During  the  period  of  fifteen  to 
twenty  days,  the  percentage  of  solids  in  the  stones  nearly 
trebled.  The  fact  is  also  brought  out  that  though  the  average 
weight  of  the  pit  (stone  and  kernel  combined)  is  only  7  per 
cent  of  the  weight  of  the  whole  fruit,  the  total  solids  in  the 
pits  comprise  more  than  25  per  cent  of  the  total  solids  in  the 
whole  fruit. 

"  It  is  well  to  observe  also  that  solids  in  the  flesh  remained 
fairly  constant  throughout  the  development  of  the  fruit, 
the  variation  ranging  from  a  total  of  14  to  about  17  per 
cent,  a  difference  of  only  3  per  cent,  while  the  solids  in 
the  stones  constantly  increased  from  about  9.3  per  cent  at 
1  Gould,  H.  P.    Loco  cit. 


'^vs^&  «»**-^*»V' 


-^  -^^#:*^i^«^^^ 


Plate  III. — a,  Dwarf  ajiplc  trees  trained  in  a  horizontal  cordon,  es- 
palier pear  trees  on  wall  to  rear,  b,  A  tj-pe  of  central  leader  that 
could  now  be  developed  either  into  a  two-  or  a  three-story  tree, 
c,  An  unpruned  apple  tree  that  has  developed  as  a  central  leader; 
recently  the  top  has  been  removed,  d,  A  two-story  tree  with  four 
branches  at  each  scaffold;  the  leader  may  now  be  removed. 


THE  THINNING  OF  FRUIT  117 

the  June  drop  period  to  nearly  67  per  cent  at  the  market 
ripe   period. 

"These  figures,  therefore,  furnish  a  scientific  basis  for 
early  thiiming,  also  for  the  frequent  observation  that  the 
development  of  a  large  number  of  pits  makes  a  heavy  de- 
mand for  plant  food." 

Experience  dictates  the  item  listed  mider  3  and  it  re- 
quires no  further  explanation. 

Some .  writers  suggest  that  the  trees  should  be  thinned 
twice  or  thrice,  the  first  time  after  the  June  drop,  the  second 
about  the  middle  of  August,  and  the  third  about  three  weeks 
before  picking,  because  the  operator  is  not  likely  to  thin 
sufficiently  the  first  time  over  the  trees.  Doubtless  it  will 
seem  necessary,  especially  to  the  begimier,  to  go  over  the 
trees  at  least  twice  in  order  to  secure  best  results,  but  this 
is  not  likely  to  be  possible  on  large  scale  orcharding. 

With  some  early  varieties  such  as  the  Yellow  Transpar- 
ent, it  may  be  desirable  to  allow  all  the  fruits  to  develop  for 
a  while  and  gradually  thin  the  crop  by  making  several  pick- 
ings. The  apples  can  be  sold  when  quite  small  as  this  va- 
riety is  merchantable  when  only  a  third  or  half  grown. 

103.  The  June  drop  referred  to  above  is  a  natural  ab- 
scission of  the  fruit  which  occurs  at  the  time  the  permanent 
fruits  are  setting.  That  is,  many  fruits  will  start  to  develop 
and  later  fall.  The  explanation  usually  offered  for  this  oc- 
currence is  that  the  fruit  is  imperfectly  pollinated;  or  it  has 
been  injured  by  insect  or  fungus  disease;  or  the  struggle  for 
existence  that  may  operate  against  a  portion  of  the  fruits 
in  a  cluster.  Often  it  is  greatly  increased  by  adverse 
weather  conditions  at  bloom  time.  Usually  the  central  blos- 
som in  a  cluster  opens  first  and  when  the  fruit  is  set  remains 
on  the  tree. 

Peach-  and  plum-growers  need  no  further  evidence  than 
they  already  possess  that  the  curculio  is  responsible  for  a 


118  POMOLOGY 

large  part  of  the  drop  many  seasons.  If  the  larva  works 
into  the  soft  pit  the  fruit  drops  very  soon,  while  if  it  enters 
only  into  the  flesh  the  fruit  may  develop  for  a  time  and  then 
show  color  as  if  ripening  and  drop  to  the  ground. 

In  some  sections,  the  apple-scab  fungus  causes  a  serious 
non-setting  of  fruit  and  early  dropping.  The  fungus  girdles 
the  tender  stems  and  prevents  the  development  of  the  crop. 

104.  How  to  thin. — In  the  operation  of  thinning  the 
apple  and  pear,  the  surplus  may  be  removed  by  holding  the 
cluster  or  spur  and  carefully  and  quickly  giving  the  fruit  an 
upward  twist.  A  special  type  of  shears  is  on  the  market 
that  is  convenient  in  cutting  the  stems,  but  usually  the  op- 
erator prefers  to  thin  by  hand.  With  the  plum  and  peach, 
the  operation  is  still  simpler — just  pick  off  the  surplus  fruits 
with  the  thumb  and  forefinger.  Rakes  and  poles  sometimes 
used  to  remove  the  surplus  are  not  to  be  recommended,  al- 
though such  an  operation  is  much  cheaper.  The  objection 
is  that  no  discrimination  can  be  made  between  good  and 
poor  fruits.  Shaking  the  tree  is  also  a  poor  way  to  accom- 
plish the  desired  results.  The  most  outstanding  warning 
that  can  be  given  is  to  avoid  breaking  the  fruit-spurs.  Va- 
rieties vary  in  the  ease  with  which  they  are  thinned.  The 
Rome  apple,  for  example,  because  of  the  long  stems,  can 
be  removed  very  rapidly,  while  the  York  is  difficult  and 
slow  to  work  because  of  the  short  stems  and  ease  with  which 
the  spurs  are  broken. 

It  should  be  recognized  that  considerable  thimiing  may 
result  when  the  trees  are  pruned,  but  with  such  fruits  as 
bear  their  entire  crop  from  axillary  buds,  additional  thin- 
ning must  be  practiced. 

105.  Distance  to  thin. — No  definite  rule  can  be  given 
for  the  distance  apart  that  fruit  should  be  thinned.  Usually 
apples  should  be  from  five  to  eight  inches  apart  and  peaches 
from  four  to  six  inches.    Beach  recommends  that  apples  be 


THE  THINNING  OF  FRUIT  119 

thinned  to  three  times  the  diameter  of  the  largest  fruits  at 
maturity  while  Wickson  suggests  that  two  and  a  half  times 
the  diameter  of  the  fruit  desired  would  be  the  proper  dis- 
tance. Herrick  found  it  desirable  to  thin  Winesap  to  nine  or 
ten  inches  apart  for  the  best  results.  Of  course,  the  smaller 
the  fruit,  the  more  it  should  be  thinned,  and  conversely 
the  larger  the  fruit  by  nature  the  less  it  should  be  thinned, 
except  to  prevent  the  breaking  of  branches. 

In  some  regions,  the  recommendation  is  to  remove  all 
fruit  from  alternate  spurs  in  order  to  bring  about  annual 
bearing.  In  all  cases  the  thimiing  should  be  uniform  and 
the  work  thoroughly  done  as  the  operation  progresses,  to 
insure  satisfactoiy  results. 

106.  Cost  of  thinning  versus  returns. — The  task  of 
thinning  a  large  orchard  of  mature  trees  when  they  have  set 
a  heavy  crop  of  fruit  seems  formidable  and  the  question 
naturally  arises  as  to  whether  it  will  pay.  However,  if  the 
cost  is  computed  to  a  tree  basis  or  to  a  still  smaller  unit,  the 
barrel  or  box,  it  will  not  seem  impracticable.  It  will  de- 
pend, of  course,  largely  on  how  the  fruit  is  to  be  handled. 
The  cost  of  thimiing  reduces  itself  to  a  question  of  time  since 
no  particular  apparatus  is  necessary,  and  this  will  depend 
on  the  size  and  shape  of  the  tree,  the  variety,  and  the  person 
doing  the  work. 

Since  the  factors  are  so  variable  in  this  regard,  it  is  diffi- 
cult to  average  conditions,  but  the  following  cases  are  cited : 

New  Hampshire.  Trees  35  years  old.  Average  4^  hours 
to  a  tree  in  one  case  (4  trees).  Average  2yi  hours  to  a  tree 
in  another  case  (4  trees). 

New  York.    Average  33^^  hours  to  a  tree  (4  mature  trees), 

Ohio.     Trees  17  years  old;     1%  to  2^  hours  to  a  tree. 

West  Virginia.  Middle-aged  trees  bearing  4  to  6  barrels 
to  the  tree.    Average    2  to  3  hours  to  a  tree. 

Colorado.    Average  a  little  less  than  3  hours  to  a  tree. 


120  POMOLOGY 

Hence,  if  it  requires  from  two  to  three  hours  to  thin  a  tree, 
the  cost  can  readily  be  computed. 

It  is  obviously  unfair  to  charge  all  the  cost  against  thin- 
ning, since  the  same  apples  would  have  to  be  picked  in  the 
fall  and  at  a  greater  expense,  and  also  it  would  require  more 
handling  of  inferior  fruit  and  greater  grading  expense  than 
when  thinning  is  practiced. 

107.  Thinning  the  peach. — Peach  trees  are  much  inclined 
to  heavy  bearing  and,  as  a  result,  the  trees  often  suffer  dam- 
age and  the  fruit  runs  small.  This  heavy  bearing  is  largely 
due  to  the  nature  of  the  fruiting  wood.  Although  a  part  of 
the  fruit-buds  may  be  removed  by  pruning,  many  more 
fruits  are  frequently  suffered  to  remain  than  the  tree  can 
properly  mature.  "There  is  perhaps  no  other  operation 
concerning  the  desirability  of  which  there  is  a  inore  complete 
oneness  of  opinion  among  peach-growers  than  in  regard  to 
thimiing  when  the  trees  are  overloaded."  ^  The  principles 
involved  in  peach  thinning  are  covered  in  the  treatment 
preceding. 

Close  ^  reports  on  thinning  the  peach  with  decided  re- 
sults in  increasing  the  size  of  the  fruit.  The  trees  were  five 
years  old  (Elberta)  and  in  vigorous  condition.  He  classi- 
fies his  thinning  as  follows:  "  Common  thimiing  means  that 
at  maturity  the  fruit  should  be  four  inches  apart;  'me- 
dium' means  six  inches  apart,  and  'severe'  eight  inches  apart 
when  ripe."  He  also  thinned  part  of  the  trees  early  and 
others  late: 

1  Gould,  H.  P.    Loco  cit. 

2  Close,  C.  P.    Ann.  Rept.  Del.  Agr.  Exp.  Sta.    1902.    p.  89. 


THE  THINNING  OF  FRUIT 


121 


Table  XXIV 
record  of  ripe  fruit  from  thinned  and  unthinned  trees  (after 
close) 


Kind  of  thinning 

Fancy, ^ 
per  cent 

Firsts,^ 
per  cent 

48 
51 
60 
80 
47 
SO 
73 

49 

Early  common 

Early  medium 

47 
39 
20 

Late  common 

Late  medium 

Late  severe 

50 
20 
26 

108.  Thinning  the  plum. — Experience  has  differed  in  the 
advantages  secured  by  thinning  plums.  In  some  places 
very  good  results  were  obtained  in  increasing  the  size  of 
the  fruit,  while  in  others  the  increase  was  almost  nothing. 
Some  varieties  fruit  so  heavily,  however,  that  it  would  be 
well  to  thin  to  prevent  the  trees  from  breaking  and  to  re- 
duce disease  and  insect  injuries. 

Garcia 's  ^  work  showed  that  definite  results  were  ob- 
tained by  thinning  plums  to  six  inches  apart  and  to  a  less 
extent  to  three  inches.  The  trees  thinned  to  six  inches  pro- 
duced on  the  average  84.1  per  cent  of  first-grade  fruit,  those 
to  three  inches  77.6  per  cent,  and  the  unthimied  trees  50.5 
per  cent: 

'  Fancy,  above  2J^  inches  in  diameter. 

2  First  grade,  21^  inches  or  slightly  less  in  diameter. 

3  Garcia,  F.    New  Mexico  Agr.  Exp.  Sta.  Bull.  39.    1901. 


122 


POMOLOGY 


Table  XXV 

THINNING    THE    PLUM    (AFTER    GARCIA) 


Name 


Distance 

thinned  in 

inches 


Percentage  of 

first-class 

fruit 


Percentage  of 

second-class 

fruit 


Wild  Goose. 


Clyman . 


Tragedy . 


Yellow  Egg . 


3 

None 


3 

None 

6 
3 

None 


3 

None 


75.7 
70.1 
67.4 

93.4 
85.9 
53.7 

86.4 
96.9 
53.7 

81.1 
57.5 

27.5 


24.2 

28.8 
32.5 

6.5 
14. 

46.2 

13.5 
3. 

46.2 

15.9 
30.6 

53. 


On  the  other  hand,  Powell  reports  on  thinning  trees  of 
the  Burbank  and  Poole's  Pride  varieties,  neither  of  which 
was  a  financial  success.  It  cost  ten  cents  a  tree  to  thin  the 
former  and  fifteen  cents  for  the  latter.  "There  was  some 
difference  in  the  size  of  fruit  in  favor  of  the  thinned  trees 
(Poole's  Pride),  but  the  difference  was  surprisingly  small. 
However,  the  unthinned  trees  suffered  very  heavily  from 
broken  branches  the  latter  part  of  the  summer  which 
did  not  occur  with  the  thinned  trees.  As  far  as  the 
crop  was  concerned  the  thinning  was  not  a  financial 
success." 

109.  Thinning  the  pear. — Not  many  data  are  available 
on  the  thinning  of  pears,  but  there  is  no  reason  to  suppose 
that  they  would  not  respond  if  the  trees  had  set  a  heavy 


THE  THINNING  OF  FRUIT  123 

crop.  Powell  ^  records  an  experiment  with  Kieffer  pears  in 
whicli  trees,  eight  years  of  age,  were  thinned.  The  trees 
had  set  full  and  the  fruits  were  removed  so  that  no  two 
were  closer  than  six  inches.  As  a  result,  83  per  cent  of  the 
thimied  pears  and  61  per  cent  of  the  check  pears  were  of 
the  No.  1  grade. 

110.  Thinning  the  grape. — Husmann  ^  says:  "It  will 
sometimes  be  necessaiy  to  thin  the  grape,  in  order  to  more 
thoroughly  develop  the  remaining  bunches.  The  best 
thinning  is  the  reduction  of  bunches  and  bearing  shoots, 
at  the  first  sunnner-pruning.  If  the  nmnber  of  bunches 
on  each  fruit-bearing  branch  is  reduced  to  two,  it  will  do  no 
injury,  but  make  them  so  much  more  heavy  and  perfect." 

Bioletti  ^  reconnnends  thinning  the  grape  in  California 
as  follows:  "This  excessive  compactness  can  be  pre- 
vented by  thinning  before  the  berries  are  one-third  grown. 
Thinning,  moreover,  increases  the  size  of  the  berries,  hastens 
ripening,  promotes  coloring,  and  lessens  some  forms  of 
sunburn.  .  .  .The  bunches  are  thinned  at  any  time  after 
the  berries  have  set  and  before  they  have  reached  one-third 
their  mature  size.  No  bunches  are  removed,  but  only  a 
certain  proportion  of  the  berries  of  each  bunch.  The  number 
of  lierries  to  be  removed  will  depend  upon  how  compact  the 
unthhmed  bunches  usually  become.  In  general  it  will  vary 
from  one-third  to  one-half  of  the  total  number.  ..." 
This,  it  will  be  noted,  refers  to  the  European  grape  (Vitis 
vinifem)  as  grown  in  California,  and  the  same  recommenda- 
tions follow  when  V.  vim f era  is  grown  under  glass  in  the 
East. 

>  PoweU,  G.  H.    Del.  Agr.  Exp.  Sta.    12th  Ann.  Rept.    1900.    p.  140. 
-  Husmann,  George.     American  Grape  Growing  and  Wine  Making. 
1883. 
3  Bioletti,  F.  T.    Stand.  Cyc.  of  Hort.  III.    p.  1385. 


CHAPTER  VII 
ORCHARD  SOILS 

Students  of  every  phase  of  plant  production,  from,  the 
extreme  specialist  in  the  greenhouse  to  the  extensive  grower 
of  field  crops,  find  a  common  interest  in  a  study  and  under- 
standing of  the  soil.  The  most  casual  observation  shows 
that  soils  vary  in  their  nature  or  physical  make-up  and 
that  plants  flourish  differently  on  the  types.  Researches 
during  the  past  quarter  of  a  century  have  added  greatly 
to  the  knowledge  of  this  subject  and  have  opened  up  numer- 
ous new  phases  which  must  be  considered  by  the  student 
of  soil  science.  It  is  not  possible  nor  desirable,  however,  to 
enter  into  a  full  discussion  of  the  properties  of  soils  in  this 
connection,  but  a  brief  outline  of  the  types  that  commonly 
occur  in  the  fruit  regions  should  be  reviewed. 

111.  Factors  involved. — It  is  of  course  true  that  several 
factors  must  enter  into  consideration  when  selecting  an 
orchard  site.  The  location  of  the  land  as  regards  market 
conditions  is  of  such  great  practical  importance  that  a 
less  valuable  soil  may  be  chosen  in  order  to  meet  this  re- 
quirement. Also  the  elevation  in  order  to  obviate  frosts 
must  be  considered.  An  otherwise  good  slope  may  be  so 
"seepy  "  owing  to  the  geological  formation  that  its  use  for 
orcharding  is  prohibitive  without  drainage.  Also  the  pre- 
vious treatment  of  the  land  and  the  supply  of  humus  and 
calcareous  material  may  greatly  affect  the  desirability  of 
the  land  for  fruit-growing.  Aside  from  these  features,  how- 
ever, the  mechanical  or  physical  make-up  of  the  soil  is 
fundamental  and  worthy  of  careful  study.  Fortunately 
124 


ORCHARD  SOILS  125 

most  fruit-trees  will  flourish  over  a  rather  wide  range  of 
soil  types  but  some  are  better  than  others  and  some  types 
are  to  be  avoided  entirely.  The  classification  of  soils  accord- 
ing to  the  usual  standard  should,  therefore,  be  considered 
first. 

112.  Soil  defined. — Soil  has  been  described  as  "the 
broken  and  weathered  fragments  of  rock  that  cover  in  a 
thin  layer  the  solid  part  of  the  earth  and  that  furnish  the 
foothold  and,  in  part,  the  sustenance  for  plant  life."  ^  An 
understanding  of  the  soil  has  involved  a  many-sided  and 
complex  investigation,  for  soils  vaiy  in  an  almost  infinite 
number  of  ways  and  the  adaptation  of  various  kinds  of 
plants  to  a  given  soil  is  far  from  constant.  These  conditions 
involve  on  the  student  of  pomology  a  necessity  for  study 
of  soil  conditions  as  a  basis  for  orchard  production. 

113.  Soil  classification. — As  regards  origin,  soils  are 
classed  as  either  "sedentary  "  or  "transported,"  depending 
on  their  geological  histoiy.  Soils  are  composed  of  minute 
particles  of  the  various  minerals  of  which  the  rocks  of  the 
earth  are  made  up  and  the  fineness  with  which  they  are 
ground,  together  with  the  proportionate  mixture  of  these 
particles,  gives  a  basis  for  classification.  The  method  of 
arriving  at  this  information  is  called  a  mechanical  analysis. 

Four  general  groups  of  soil  particles  are  recognized  in 
agriculture  as  a  basis  of  classification:  sand,  silt,  clay,  and 
humus.  The  size  of  the  particles  composing  each  of  these 
series  has  been  standardized  by  the  United  States  Bureau 
of  Soils  as  follows: 

Coarse  sand  1/25  to  1/50        of  an  inch  in  diameter. 

Medium  sand  1/50  to  l/lOO     "    "      "      " 

Fine  sand  l/lOO  to  1/250  "    "      "      " 

Very  fine  sand  1/250  to  1/500   "    "      "      " 

1  Lyon,  Fippin,  Buckman.  Soils,  Their  Properties  and  Manage- 
ment.    New  York,  1915.    Rural  Text-Book  Series. 


126  POMOLOGY 

Silt  1/500  to  1/2000  of  an  inch  in  diameter. 

Fine  silt  1/2000  to  1/5000  "    "      ''      " 

Clay  1/5000  to  1/250,000  ''  "      "      " 

Sand  is  a  valuable  component  of  an  orchard  soil,  although 
in  itself  it  does  not  contain  plant-food,  since  the  sand  par- 
ticles are  largely  quartz  which  weathers  very  slowly.  It 
is  of  value  because  it  lightens  the  soil,  gives  it  natural  drainage 
and  has  a  tendency  to  make  it  warm. 

Clay  is  composed  of  very  small  particles,  microscopic  in 
size,  and  forms  to  a  considerable  extent  the  body  of  the  soil. 
It  is  derived  from  various  rocks  and  carries  considerable 
of  the  mineral  elements  of  plant-food.  The  colloids  of  the 
soil,  which  have  recently  received  considerable  attention, 
are  associated  with  the  finer  clay  particles.  If  clay  is  present 
in  abundance,  the  soil  will  diy  badly,  shrink,  and  crack 
during  very  dry  periods.  On  the  other  hand,  clay  causes 
the  soil  to  be  heavy  and  difficult  to  work  when  wet. 

Silt  is  much  the  same  as  clay  in  its  character  but  the 
particles  are  intermediate  in  size  between  the  sands  and 
clay.  A  soil  containing  large  amounts  of  silt  is  usually 
moderately  rich,  well  adapted  to  the  growing  of  the  grain 
crops. 

Humus  is  a  term  given  to  decomposed  vegetation  and  is 
of  signal  value  in  increasing  the  water-holding  capacity  of 
a  soil  and  in  causing  it  to  be  mellow  and  easy  to  work.  This 
term  is  often  used  loosely  or  incorrectly,  since  vegetation 
plowed  into  the  soil  does  not  become  humus  until  it  is 
thoroughly  decayed.  The  humic  acids  produced  during 
decay  contribute  materially  to  the  setting  free  of  plant- 
food  m'aterials  in  the  soil. 

The  term  loam  is  used  to  describe  a  soil  made  up  of  a 
combination  of  sand,  silt,  and  clay  and  it  is  further  defined 
by  the  predominance  of  one  or  the  other,  as  sandy  loam, 
silt  loam,  or  clay  loam.     The  fruit-grower  is  interested  in 


ORCHARD  SOILS  127 

the  various  loam  soils,  depending  on  the  kind  and  variety 
of  fruit  grown. 

When  the  clay  and  silt  particles  predominate,  only  the 
fine  grades  of  sand  are  usually  present.  If  the  silt  grade  is 
most  abundant,  the  soil  is  a  silt  loam.  If  clay  is  greatest 
in  amount,  the  soil  is  a  clay  loam.  And  if  the  exceedingly 
fine  clay  particles  constitute  more  than  30  per  cent  of  the 
soil  mass,  the  type  is  a  clay,  the  other  70  per  cent  being 
primarily  of  silt  and  very  fine  sand.  A  soil  containing  as 
nuich  as  50  per  cent  clay  is  very  "heavy,"  while  those  con- 
taining 60  to  70  per  cent,  as  at  Medford,  Oregon,  are  ex- 
ceedingly stiff  and  hard  to  work.-^ 

114.  Soils  and  subsoils. — Most  soils  consist  of  a  surface 
layer  which  is  more  fertile  and  usually  darker  colored  than 
those  l>ing  beneath  it.  It  may  be  veiy  shallow  or  a  foot 
to  many  feet  in  thickness.  This  surface  soil  determines  the 
richness  of  the  land,  since  the  roots  of  most  crops  penetrate 
but  little  below  it.  Its  fertility  is  due  to  the  larger  amounts 
of  organic  matter  and  the  accumulation  of  the  more  readily 
available  plant-foods,  together  with  the  activity  of  the 
beneficial  soil  flora.  The  subsoil,  or  that  which  Ues  im- 
mediately beneath  the  surface,  is  of  great  importance  to 
the  fruit-grower  and  its  character  may  vaiy  from  a  sand  to 
an  impervious  clay  known  as  hardpan.  The  tree  roots 
should  have  a  wide  range  and  penetrate  the  subsoil  with 
ease  as  well  as  be  free  from  standing  water.  While  the 
subsoil  must  not  be  too  well  drained  and  devoid  of  plant- 
food,  yet  an  open  gravelly  loam  is  usually  considered  best. 
If  this  does  not  obtain,  it  may  be  necessary  to  tile  drain  and 
plow  or  break  up  the  subsoil  for  best  results.  The  time  to 
solve  this  problem  or  rather  to  avoid  difficulty  is  when  the 
orchard  land  is  selected. 

The  necessity  for  good  depth  of  subsoil  cannot  be  empha- 
1  Wilder,  H.  J.    U.  S.  Dept.  Agr.  Bull.  140.    1915. 


128  POMOLOGY 

sized  too  strongly.  This  applies  to  every  variety  of  apple 
or  other  tree-fruit  and  to  every  type  of  soil.  Shallow  soils 
should  be  assiduously  avoided  for  orchard  purposes  wherever 
they  occur.  The  presence  of  unbroken  rock,  large  ledges, 
or  hardpan  within  three  feet  of  the  surface  should  be  con- 
sidered prohibitive.  A  soil  depth  of  at  least  six  feet  should 
be  insisted  on  wherever  possible  and  an  even  greater  depth 
is  highly  desirable. 

Most  of  the  fruit  sections  in  America  contain  some  soils 
adapted  to  fruit-growing  and  others  that  give  indifferent 
or  poor  results.  Not  infrequently  the  nature  of  the  subsoil 
is  the  cause  of  the  failures,  for  it  must  be  remembered  that 
trees  are  comparatively  deep-rooted. 

While  many  sections  might  be  taken  for  illustration,  the 
extensive  fruit  region  known  as  the  "Ozarks"  may  be  cited 
or  a  certain  part  of  it  which  lies  in  the  Arkansas  Valley. 
Three  types  of  subsoils  are  found  through  that  general  sec- 
tion. The  good  fruit  subsoils  vary  from  dark  brown  to  a 
light  reddish  brown  in  color  and  are  formed  from  broken 
granite.  The  deposit  of  this  material  varies  from  a  few 
inches  to  several  feet  in  depth,  holds  moisture  well,  but  also 
drains  well,  and  hence  is  good  fruit  land.  Another  type  is  a 
gravel  subsoil  which  leaches  badly  and  is  likely  to  suffer  in 
dry  weather  unless  irrigated.  A  third  type,  on  which  many 
orchards  have  been  inadvertently  set,  consists  of  the  finest 
of  soil  particles  and  hence  affords  poor  drainage.  The  roots 
seem  unable  to  penetrate  this  soil  and  the  trees  suffer  from 
droughts,  root-rot,  and  widespread  winter-injury.  Inciden- 
tally, much  of  the  difficulty  can  be  avoided  if  alfalfa  is 
planted,  as  the  roots  of  this  plant  penetrate  the  subsoil. 

115.  Mechanical  analysis  of  fruit  soils. — The  texture 
of  a  few  typical  fruit  soils  may  now  be  exammed.  No  one 
type  of  soil  is  essential,  since  fortunately  most  fruit-trees 
have  a  fairly  wide  range  of  adaptability,  but  it  will  be  seen 


ORCHARD  SOILS  129 

that  in  general  the  loam  or  gravelly  soils  when  underlaid  by- 
one  not  too  heavy  are  frequently  best  adapted  to  fruit- 
growing. The  kind  and  variety  of  fruit  to  be  grown  must 
be  considered  in  determining  whether  the  heavier  or  lighter 
types  of  soils  should  be  selected.  The  light  sandy  soils  are 
ideal  to  work,  but  they  do  not  hold  the  soluble  plant-foods 
so  well  and  are  likely  to  suffer  in  times  of  drought. 

In  western  New  York,  the  apple  soils  are  a  little  heavier 
than  those  in  many  other  sections.  The  trees  attain  very 
large  size  and  give  high  yields.  In  Niagara  County,  which 
l)roduces  a  large  amount  of  fruit,  the  Dunkirk  loam  is  typi- 
cal of  the  best  fruit-soils.  "Besides  general  crops,  a  very 
large  acreage  of  this  type  (of  soil)  is  devoted  to  fruit  pro- 
duction. Throughout  the  county  it  (the  Dunkirk  loam)  is 
distinguished  by  the  prevalence  of  apple  orchards.  In  the 
southern  part  the  small  area  may  almost  universally  be 
recognized  by  the  presence  and  condition  of  the  orchards. 
The  trees  have  made  a  good  growth  and  are  regular  in  form 
and  thrifty  in  appearance.  While  other  types  may  pro- 
duce good  apples,  the  opinion  of  a  large  number  of  apple 
buyers  and  packers  is  that  apples  grown  on  this  soil  are 
of  superior  flavor,  color,  and  keeping  quality.  .  .  While 
the  peach  thrives  on  a  soil  much  lighter  than  is  suitable 
for  the  apple,  it  is  said  by  a  number  of  practical  men  that 
on  this  soil  is  obtained  fruit  superior  in  flavor,  color,  and 
keeping  quality.  Pears,  plums,  and  quinces  are  grown  and 
west  of  Lockport  there  is  a  large  acreage  of  grapes."^ 

The  following  table  gives  the  mechanical  analysis  of  this 
soil: 

1  U.  S.  Bureau  SoUs.     1906. 


130 


POMOLOGY 


Table  XXVI 

DUNKIRK  LOAM,  NIAGARA  COUNTY,  NEW  YORK 


Fine 
gravel 

Coarse 
sand 

Medium 
snnd 

Fine 
sand 

Very 
fine 
sand 

Silt 

Clay 

Soil 

Subsoil 

0.9 
.0 

4.2 
1.7 

3.3 
1.4 

6.4 
5.5 

13.5 
4.3 

52.9 
54.9 

18.4 
32.1 

In  Ontario  County,  which  is  also  in  the  fruit  belt  of  west- 
ern New  York,  the  best  fruit  is  grown  on  the  Ontario  loam 
which  is  somewhat  lighter  and  has  the  following  mechanical 
analysis: 

Table  XXVII 

ONTARIO  LOAM,  ONTARIO  COUNTY,  NEW  YORK 


Fine 
gravel 

Coarse 
sand 

Medium- 
sand 

Fine 
sand 

Very 
fine 
sand 

Silt 

Clay 

Soil                

1.0 
1.1 

3.0 
4.0 

4.5 
5.4 

12,8 
14.5 

14.6 
19.0 

47.5 
39.6 

16  1 

Subsoil 

16.3 

Fort  Valley  is  the  center  of  the  peach  industry  of  Georgia 
and  one  of  the  best  known  peach  sections  of  the  coun- 
try. The  soils  best  adapted  to  the  production  of  this  fruit 
are  the  Orangeburg  sandy  loam  and  the  Orangeburg  fine 
sandy  loam.  The  fruit  grown  on  these  soils  is  superior  to 
that  on  any  of  the  other  soils  of  that  area.  The  latter  is 
ranked  as  the  best  peach  soil  of  the  whole  Gulf  Coastal 
Plain  region,  owing  to  "the  inherent  characteristics  of 
the  soil  itself  and  to  the  elevated  and  well  drained  posi- 
tion it  normally  occupies."  Elberta  is  the  variety  typically 
grown. 


ORCHARD  SOILS 


131 


Table  XXVIII 

ORANGEBURG  SANDY  LOAM 


Fine 
gravel 

Coarse 
sand 

Medium 
sand 

Fine 
sand 

Very 
fine 
sand 

Silt 

Clatj 

Soil 

Subsoil 

1.90 

.52 

6.90 
3.42 

6.68 
4.44 

27.10 
21.86 

40.40 
29.56 

10.28 
9.00 

6. 28 
30.50 

In  comparison  with  the  Ughter  types,  the  very  heavy 
dark  soils  of  the  Rogue  River  Valley  near  Medford,  Oregon, 
on  which  the  pear  is  being  grown  very  extensively,  should 
be  considered.  A  number  of  types  of  soil  occur  in  the  valley 
and  foothills  which  are  adapted  to  the  growing  of  pears  and 
apples,  the  Phoenix  clay  adobe  being  one  of  the  heavier 
kinds.  Some  of  the  most  valuable  orchards  in  the  valley 
are  on  this  soil. 


Table  XXIX 

PHCENIX  CLAY  ADOBE 


Fine 
gravel 

Coarse 
sand 

Medium 
sand 

Fi7ie 
sand 

Very 
fine 
sand 

sat 

Clay 

Soil 

0.9 

2.4 

2.2 

4.1 

5.7 

21.4 

63.1 

This  soil  is  12  inches  to  six  feet  or  more  in  depth,  of  a  dark 
reddish  brown  to  nearly  black,  sticky,  and  of  a  pronounced 
adobe  structure. 

The  soil  in  the  Hood  River  (Oregon)  district  is  much 
lighter  and  well  adapted  to  apples.  It  is  essentially  a  loam 
with  a  high  percentage  of  very  fine  sand.  The  subsoil  is 
much  the  same  in  character  except  in  places  where  it  be- 
comes very  compact  and  not  suited  to  orcharding. 


132 


POMOLOGY 


Table  XXX 

HOOD    SILT   LOAM 


Fine 
gravel 

Coarse 
sand 

Medium 
sand 

Fine 
sand 

Very 
fine 
sand 

Silt 

Clay 

Soil 

0.4 
.1 

2.4 

.8 

4.8 
1.9 

9.6 

7.8 

20.3 
26.6 

48.8 
42.8 

13.6 

Subsoil 

19.8 

From  these  examples  it  will  be  seen  that  there  is  a  rather 
wide  range  of  fruit  soils,  although  as  a  rule  those  which  ap- 
proximate the  following  analysis  are  best  adapted  to  most 
fruits : 

Per  cent 

Aggregate  of  all  sands 20-50 

Silt 20-50 

Clay 10-30 

Hall  and  Russell  give  the  following  as  an  ideal  fruit  soil: 

Per  cent 

Fine  gravel 1.0 

Coarse  sand 6.8 

Fine  sand 42.0 

Silt 23.3 

Fine  silt 7.3 

Clay 10.9 

116.  Orchard  soils. — Since  an  orchard  soil  is  judged 
more  from  its  mechanical  make-up  than  from  its  chemical 
constitution,  it  may  be  well  to  define  further  the  types  best 
adapted  to  the  several  fruits.  It  is  impossible  to  state  within 
narrow  limits  just  what  may  be  termed  an  orchard  soil. 
Indeed,  perhaps  a  fourth  or  a  third  of  the  arable  land  of  this 
country  might  be  used  with  considerable  success  for  orchard- 
ing if  other  factors  were  favorable.  While  analyses  have 
been  given  of  a  few  typical  orchard  soils,  the  list  might  be 


ORCHARD  SOILS  133 

greatl.y  extended.  In  a  very  general  way  the  following  are 
usually  requisites: 

(1)  The  soil  should  be  sufficiently  retentive  of  moisture 
so  that  the  trees  and  crop  will  not  suffer  from  lack  of  water 
throughout  the  growing  season,  or  else  irrigation  should  be 
available. 

(2)  Fruit  soils  should  usually  be  of  a  rather  open  nature 
so  that  ample  drainage  is  provided;  the  texture  being  porous 
and  friable. 

(3)  The  soil  should  not  be  low  in  organic  matter. 

(4)  Extremes  of  acidity  and  alkalinity  should  be  avoided. 

(5)  A  depth  of  not  less  than  six  feet  is  highly  desirable. 
The  apple  in  general  thrives  on  an  open  gravelly  or  light 

clay  loam,  although  it  succeeds  on  both  heavy  and  quite 
light  soils.    Varieties  differ  in  their  requirements. 

Pears  as  a  class  prefer  a  heavier  type  of  soil  than  the  apple, 
but  the  "adobe"  soils  of  southern  Oregon  represent  an  ex- 
treme rather  than  the  usual  type.  On  a  heavy  silt  or  clay 
loam  they  are  at  their  best. 

The  peach  and  cherry  prefer  a  gravelly  or  heavy  sandy 
loam,  but  in  some  sections  the  soil  runs  to  a  heavier  type, 
even  approaching  a  clay.  The  one  requisite  in  all  cases  is 
good  drainage. 

The  domestica  plums  should  be  grown  on  a  moderately 
rich  loamy  soil,  and  the  salicina  varieties  on  a  somewhat 
lighter  type. 

Much  has  been  said  in  literature  regarding  the  value  of 
stony  land  for  orchard  purposes.  This  idea  doubtless  has 
its  origin  in  the  fact  that  well-drained  soils  are  preferable 
and  also  that  orchards  are  frequently  successful  on  stony 
or  rocky  hillsides.  There  can  be  no  virtue  in  such  land 
other  than  the  fact  that  an  abundance  of  stones  may  give 
ample  drainage  and  produce  a  loose  type  of  soil  and  per- 
haps  that  a  quantity  of  stones  may  serve  as  a  mulch 


134  POMOLOGY 

and  conserve  moisture.  If  a  stony  soil  is  selected,  and  it 
frequently  is  very  satisfactory,  it  should  be  fertile  and 
productive. 

117.  Chemical  nature  of  fruit  soils. — It  is  generally 
agreed  that  the  mechanical  make-up  or  texture  of  the  soil 
is  even  more  important  than  its  fertility,  since  it  is  more 
difficult  to  change  materially.  However,  it  is  a  mistaken 
notion  that  the  poorest  soils  should  be  selected  for  fruit- 
trees.  This  is  true  in  spite  of  the  fact  that  some  kinds  of 
fruit  can  usually  be  grown  on  the  poorer  soils  with  more 
success  than  most  agricultural  crops.  It  must  also  be  rec- 
ognized that  it  is  not  entirely  the  percentage  of  mineral  ele- 
ments m  the  soil  in  available  form  that  makes  for  its  fer- 
tility, but  of  great  importance  are  the  organic  or  humus 
content  and  its  consequent  soil  flora  together  with  a  proper 
water  relation  and  the  absence  of  toxic  materials  or  "unsan- 
itary" conditions. 

A  chemical  analysis  of  agricultural  soils  shows  that  the 
following  elements  are  usually  present:  Silicon,  aluminum, 
iron,  phosphorus,  calcium,  magnesium,  sodium,  and  potas- 
sium. Sulfur  and  chlorine  are  also  found  in  small  quan- 
tities. The  nitrogen  of  the  soil,  which  is  so  important  to 
plant  growth,  is  almost  entirely  in  the  form  of  organic  mat- 
ter, although  the  soil-air  contains  small  amounts  of  the  at- 
mospheric nitrogen  and  also  more  or  less  ammonia.  Nitro- 
gen occurs  in  mineral  form  in  some  places  or  is  obtained  by 
manufacture  and  purchased  as  nitrate  of  soda,  potassium 
nitrate,  and  sulfate  of  anmionia  for  agricultural  purposes. 
If  the  silicon,  alummum,  and  sodium  are  eliminated  as  un- 
essential plant-foods,  it  leaves  but  15  per  cent  of  the  soil  as 
the  source  of  the  mineral  constitutents  of  plants. 

118.  Soil  color. — While  the  question  of  soil  color  may 
be  over-emphasized,  nevertheless  certain  characteristics 
are  correlated  with  it.     A  dark  color  usually  indicates  the 


ORCHARD  SOILS  135 

presence  of  considerable  percentage  of  organic  material  and 
this  is  usually  associated  with  a  rich  soil. 

The  Porters  black  loam  of  Virginia  and  the  Phoenix  adobe 
clay  of  Medford,  Oregon,  are  examples  of  black  soils  espe- 
cially valuable  for  fruit-growing.  Most  fruit  soils  are  not  so 
dark  in  color.  A  reddish  or  yellowish  soil  usually  indicates 
the  presence  of  a  large  amount  of  oxidized  iron.  Some  of 
the  clays  are  very  red  as  also  are  some  of  the  soils  derived 
from  sandstone  formation.  Some  of  these  are  rich  and 
productive,  but  ordinarily  the  red  color  would  not  indicate 
a  well  aerated  and  rich  soil. 

119.  Limestone  soils. — ^The  question  as  to  whether  lime- 
stone soils  are  preferable  for  fruit  is  frequently  raised.  In 
order  to  form  an  opinion,  the  function  of  lime  in  the  soil  may 
be  briefly  reviewed. 

The  function  of  lime  in  the  soil  is  two-fold:  (1)  to 
prevent  "sourness"  and  neutralize  the  aluminum  com- 
pounds; and  (2)  to  flocculate  clay  soils  and  tend  to  hold  to- 
gether the  sandy  ones.  Lime  is  looked  on  as  a  soil  "im- 
prover" but  it  is  of  course  a  plant-food,  for  it  is  present  in 
the  ash  of  all  plants  and  has  a  definite  function  to  perform. 
However,  it  is  rarely  necessary  to  apply  it  for  that  purpose 
since  all  soils  contain  some  calcium  oxide.  The  exact  per- 
centage of  lime  necessaiy  varies  with  the  nature  of  the  soil 
and  hence  is  relative.  "The  greater  the  clay  percentage 
in  a  soil,  the  more  lime  carbonate  it  must  contain  in  order 
to  possess  the  advantages  of  a  calcareous  soil ;  and  that  while 
in  sandy  lands  lime  growth  may  follow  the  presence  of  only 
.10  per  cent  of  lime,  in  heavy  clay  soils  not  less  than  about 
.6  percent  should  be  present  to  bring  about  the  same  re- 
sult." ^ 

The  adaptation  of  plants  to  soils  is  a  well-known  phenom- 
enon and  one  which  has  frequently  guided  the  agricultur- 
1  Hilgard,  E.  W.    Soils,  p.  369.    New  York.    1906. 


136  POMOLOGY 

ist  in  determining  cultural  requirements.  Some  plants  are 
distinctly  "lime-loving,"  such  as  most  of  the  legumes 
(alfalfa,  clovers),  others  are  equally  "acid-loving,"  as  the 
Heath  family  and  the  chestnut  (Castanea  dentata),  while 
others  are  cosmopolitan  so  far  as  the  soil  requirement  is 
concerned.  Among  the  fruits,  the  following  are  adapted  to 
sour  soils:  blueberry,  cranberry,  strawberiy,  blackbeny, 
and  red  and  blackcap  raspberries;  while  the  currant  is  listed 
as  injured  by  sour  soils. ^  It  would  seem  from  observation 
that  most  fruit-trees,  especially  the  apple,  stand  on  middle 
ground  so  far  as  the  lime  requirement  is  concerned.  They 
are  neither  distinctly  hme-  nor  acid-loving  (as  these  terms 
are  commonly  used)  but  flourish  in  both  types  until  the  dis- 
tinctly alkaline  soils  are  reached  on  the  one  hand  and  the 
bog  soils  on  the  other.  There  is  a  popular  belief  that  the 
apple  does  best  on  a  limestone  soil,  but  this  would  be  diffi- 
cult to  establish.  The  idea  doubtless  has  its  source  in  the 
fact  that  a  limestone  soil  is  frequently  fertile  and  that  many 
very  fine  orchards  happen  to  be  located  in  limestone  dis- 
tricts. As  a  matter  of  fact,  the  non-calcareous  soils  are 
often  preferred,  even  when  either  would  be  available.  This 
is  particularly  true  for  the  peach. 

Thus  it  is  difficult  to  find  evidence  to  answer  this  question 
in  the  affirmative  since  the  eye  does  not  detect  any  out- 
standing differences  and,  generally  speaking,  fruit-trees  do 
as  well  in  the  non-calcareous  regions  as  in  the  limestone 
areas.  It  would  seem  that  Hilgard  has  put  the  matter  too 
strongly  so  far  as  orchard  fruits  are  concerned  when  he  says, 
"The  abundant  fruiting  of  oaks  on  such  lands  as  compared 
with  the  same  species  on  non-calcareous  soils  is  a  matter  of 
common  note  in  the  Mississippi  Valley  states;  and  the  same 
is  true  of  other  trees,  and  of  herbaceous  plants  as  well."  ^ 

1  Lyon,  Fippin,  Buckman.    Soils,  p.  384.    New  York.    1915. 
^Loco   cit.    p.  503. 


ORCHARD  SOILS 


137 


There  is  also  little  evidence  in  this  countiy  to  show  that 
the  application  of  lime  to  orchard  land  has  any  appreciable 
effect  on  the  trees  or  the  quality  of  the  fruit.  Its  effect  in 
increasing  the  growth  of  cover-crops  on  certain  soils  is  quite 
another  question  and  must  at  once  be  recognized.  Indirectly 
this  may  bring  about  an  increase  in  the  growth  and  yield 
of  the  trees  as  is  discussed  in  a  later  chapter. 

120.  Alkaline  soils. — An  alkali  soil  is  one  which  is 
strongly  impregnated  with  various  salts,  such  as  sulfate, 
chlorid,  and  carbonate  of  sodium,  magnesium  sulfate,  cal- 
cium sulfate,  calcium  chlorid,  and  others.    In  some  sections 


Table  XXXI 

ALKALI  IN  SOILS  OF  ORCHARDS   (AFTER   LOUGHBRIDGE) 


Percentage 

in  soil. 

Total 

Trees 

Condition 

sulfate 

carbonate 

chlorid 

Apples 

Red  Bietigheimer 

Good 

.101 

Duchess 

Poor 

.146 

Jonathan 

Poor 

.041 

Apricots 

Good 

.063 

Affected 

.246 

Peaches 

Best 

.070 

Poor 

.106 

Poor 

.160 

Pears 

Best 

.131 

Poor 

.261 

Plums 

Very  poor 

.165 

138  POMOLOGY 

of  the  country,  this  type  of  soil  constitutes  a  serious  handi- 
cap to  fruit-growing  as  well  as  to  the  production  of  other 
crops.  Fruit  plants  vary  considerably  in  their  suscepti- 
bility to  alkali  conditions.  Loughbridge  ^  has  made  a  care- 
ful study  of  this  problem  as  shown  in  the  table  on  page  137. 

"The  (apple)  tree  is  quite  sensitive  to  alkali  salts,  and 
their  effects  on  the  foliage  of  the  tree  were  veiy  marked.  The 
Jonathan  seems  to  be  more  sensitive  than  the  Duchess." 

The  other  fruits  observed  showed  that  when  the  trees 
are  affected  by  alkali  soil  conditions,  the  newer  Hmbs  are 
more  or  less  bare  except  for  a  tuft  of  leaves  on  the  terminal, 
the  leaves  are  small,  yellowish  or  blackish  in  appearance, 
and  the  trees  are  barren  of  fruit. 

Observations  and  data  cited  show  that  "the  suscepti- 
bility of  the  wine  (grape)  varies  according  to  variety,  and 
that  while  some  are  tolerant  of  very  large  amounts  of  car- 
bonate of  soda  and  common  salt,  others  succumb  to  the 
effect  of  far  less  of  each." 

Hilgard  ^  says,  in  discussing  deciduous  orchard  trees, 
"Of  these,  strangely  enough,  the  almond  seems  to  resist 
best.  The  peach  is  more  sensitive,  the  apricot  does  fairly 
well.  Plum  trees  are  nearly  as  resistant  as  peaches,  but 
sometimes  suddenly  begin  to  fail  when  beginning  to  bear; 
the  fruit  appears  normal  on  the  outside  for  a  time,  but  the 
pit  fails  to  form,  being  sometimes  flattened  out  like  a  piece 
of  pasteboard;  and  the  fruit  fails  to  mature.  Apples  are 
rather  sensitive;  pears  considerably  less  so,  doing  well  even 
when  the  outside  bark  around  the  root  crown  is  blackened 
by  alkali.    The  olive  is  quite  resistant,  the  fig  less  so." 

121.  Drainage. — As  stated  in  paragraph  114,  the  natural 
drainage  of  the  orchard  land  is  of  the  greatest  importance 
in  maintaining  a  healthy  and  long-lived  tree.     If  the  soil  is 

1  Loughbridge,  R.  H.    Calif.  Agr.  Exp.  Sta.  Bull.  133.     1901. 

2  Calif.  Agr.  Exp.  Sta.  Bull.  128.     1900. 


ORCHARD  SOILS  139 

not  naturally  well  drained,  aitificial  drainage  may  be  very 
desirable  if  not  necessaiy.  While  kinds  and  varieties  of 
fruit  will  vary  in  their  susceptibility  to  "wet  feet,"  yet  prac- 
tically all  fruit-trees  do  poorly  if  the  land  is  regularly  soggy 
or  springy  during  any  extended  period  of  the  growing  season. 

When  artificial  drainage  is  resorted  to,  the  depth  of  the 
tiles  and  the  distance  apart  the  lines  are  placed  will  vary 
with  the  nature  of  the  soil  and  the  amount  of  water  which 
must  be  drained.  In  a  heavy  soil  the  lines  of  tile  are  com- 
monly placed  at  2  to  23^2  feet  deep,  and  about  2  rods  apart, 
while  in  a  sandy  or  gravelly  soil  the  depth  would  be  greater — 
from  3  to  33^  feet.  That  is,  the  more  open  the  soil  the  greater 
the  distance  the  drainage  water  may  be  drawn. 

122.  Organic  matter. — Probably  any  system  of  perma- 
nent agriculture  should  involve  the  returning  to  the  soil  of  a 
plant  residue  or  vegetative  matter.  This  seems  fundamental 
because  investigation  has  entirely  established  the  existence 
of  a  large  soil  flora  and  the  necessity  of  bacterial  action  for 
the  continuous  availability  of  plant-food  materials.  A  soil 
veiy  low  in  organic  matter  is  usually  of  poor  tilth  and  sup- 
ports a  stunted  tree  growth.  Also  the  returning  of  vegeta- 
tion, especially  legumes,  to  the  soil  maintains  a  much  better 
supply  of  nitrates  than  when  the  soil  receives  "clean"  til- 
lage or  is  entirely  untilled.  Many  orchard  soils  are  mate- 
rially improved  in  texture  by  plowing  in  a  rank  or  heavy 
growing  crop.  This  may  be  replaced  after  a  few  years  by 
a  nitrogenous  crop. 

The  student  should  appreciate,  however,  that  it  is  often 
a  long  and  expensive  process  to  reconstruct  a  soil  devoid  of 
humus,  or  a  heavy  intractable  clay  into  one  which  is  well 
adapted  to  orcharding.  From  an  economic  standpoint,  it 
is  better  to  select  soil  that  is  already  adapted  to  the  crop 
to  be  grown  and  then  by  reasonable  amendments  maintain 
its  fertility. 


140  POMOLOGY 

123.  Adaptation  of  fruit  to  soil  types. — As  indicated 
in  a  foregoing  paragraph,  there  is  in  nature  a  definite  adap- 
tation of  given  plants  to  certain  soils,  some  preferring  an 
acid  soil,  others  a  calcareous  one,  some  a  wet  soil,  others  an 
arid  one.  The  different  kinds  of  fruit-trees  also  manifest 
to  a  less  degree  some  soil  preferences,  or  rather  they  thrive 
better  on  one  kind  than  on  another. 

The  knowledge  in  regard  to  varietal  adaptation  to  soils  is 
not  extensive,  although  certain  outstanding  cases  have  been 
repeatedly  observed.  The  work  of  Wilder  ^  along  this  line 
is  the  most  complete  in  American  literature. 

The  previous  conception  that  the  Baldwin  apple  thrives 
best  on  a  rather  light  type  of  orchard  land  is  confirmed  by 
his  observations.  The  subsoil  should  be  somewhat  heavier 
but  not  so  clayey  as  to  be  termed  stiff.  The  Rhode  Island 
Greening,  on  the  other  hand,  produces  better  fruit  if  the 
soil  is  of  a  heavy  silty  loam  or  light  silty  clay  loam,  under- 
lain by  silty  clay  loam.  The  soil  should  be  moderately 
rich  in  organic  matter  and  retain  sufficient  moisture  to  be 
classed  as  a  moist  soil  and  yet  must  not  be  poorly  drained. 
The  "blushed"  Greening  is  produced  on  soil  which  ap- 
proaches more  nearly  the  Baldwin  type.  The  Northern 
Spy  is  veiy  exacting  in  regard  to  the  type  of  soil  on  which 
it  does  best  and  the  one  suited  to  it  seems  to  be  a  medium 
loam  underlain  by  a  heavy  loam  or  light  clay  loam,  i.  e.,  a 
soil  as  heavy  as  can  be  selected  without  incurring  danger  of 
inferior  drainage.  Much  the  same  type  of  soil  is  desirable 
for  the  Wagener.  The  heavier  of  the  Baldwin  soils  is 
recommended  for  the  Mcintosh  but  if  experience  is  to  be 
taken  as  a  guide,  this  variety  must  be  considered  rather 
more  cosmopolitan  than  many  others,  for  it  is  successfully 
grown  on  soils  ranging  from  rather  light  to  fairly  heavy  and 
even  on  those  which  are  not  very  well  drained.  Much  the 
1  See  Wilder,  H.  J.    Loco   cit. 


ORCHARD  SOILS  141 

same  is  true  of  the  Stayman.  The  Tompkins  King,  Graven- 
stein,  and  Ben  Davis  do  well  on  an  open-textured  rather 
than  a  fine  loam,  with  subsoil  of  the  same  or  only  slightly 
heavier  texture. 

For  peach  varieties  the  following  soil  types  have  been 
suggested:  Champion  succeeds  best  on  soils  of  only  me- 
dium productivity,  but  they  should  be  deep  and  well  drained. 
Medium  to  heavy  friable  sandy  loams,  underlain  by  mate- 
rial not  heavier  than  a  friable  loam  and  preferably  a  heavy 
sandy  loam,  are  veiy  desirable.  Carman  and  Mountain 
Rose  succeed  best  on  soils  somewhat  less  pervious  than  the 
Champion,  yet  deep  and  well  drained.  The  Elberta  and 
the  Belle  prefer  stronger  soils  than  the  Carman  and  the 
Mountain  Rose.  Loams,  silty  loams,  and  silt  loams,  with 
subsoils  of  similar  material  seem  best  to  meet  these  require- 
ments. For  Late  Crawford,  a  fairly  strong  soil,  such  as  a 
light  porous  loam  somewhat  less  retentive  of  moisture  than 
the  heaviest  of  the  Elberta  soils,  is  desirable. 

Some  of  the  early  varieties,  such  as  Greensboro,  are  less 
sensitive  to  shallow  soil  conditions  than  the  sorts  mentioned 
above. 


CHAPTER  VIII 
CULTURAL  METHODS  IN  ORCHARDS 

The  kinds  of  fruits  vary  in  their  requirements  as  regards 
culture,  some  bring  tolerant  of  widely  different  methods 
while  others  are  specific.  Varieties  also  differ  in  this  regard, 
some  requiring  thorough  and  annual  cultivation  while  others 
may  produce  a  satisfactory  growth  and  yield  with  less 
stimulation.  In  general,  however,  it  may  be  said  that 
fruit-trees  are  vigorous  and  productive  largely  in  proportion 
to  the  soil  treatment  that  they  receive.  Young  orchards 
in  particular  suffer  readily  from  lack  of  good  growing  con- 
ditions and  hence  delayed  bearing  of  commercial  crops  is 
the  result.  Older  trees,  while  more  tolerant  of  neglect, 
owing  to  the  greater  ramification  of  their  root  systems  and 
also  because  of  their  greater  reserve  food  materials  will, 
nevertheless,  usually  respond  readily  to  good  soil  treatment. 

Unfortunately,  authorities  do  not  entirely  agree  as  to 
the  best  methods  of  orchard  culture.  Certainly  there  is  no 
one  best  system  for  all  orchards  under  all  conditions.  How- 
ever there  are  principles  underlying  the  cultural  problems 
which  should  guide  the  student  in  deciding  what  system 
to  use. 

While  the  use  of  manures  and  artificial  fertilizers  is  inti- 
mately related  to  cultural  problems,  a  full  discussion  of 
them  must  be  considered  later,  except  as  general  statements 
require  mention. 

124.  Systems  of  cultivation. — Broadly  speaking,  two 
general  systems  of  cultivation  are  followed  in  orchard 
practice,  one  in  which  the  land  or  a  part  of  it  is  tilled  and 
142 


CULTURAL  METHODS  IN  ORCHARDS  143 

the  other  in  which  the  land  remains  permanently  in  sod. 
A  number  of  variations  of  both  these  methods  are  in  use.  If 
a  grower  has  achieved  success  with  one  or  the  other,  he  often 
becomes  prejudiced  against  the  other  systems. 

125.  Terms  defined. — Sod  culture  describes  any  system 
of  soil  management  wherein  the  trees  are  grown  in  sod 
without  tillage  of  any  kind,  or  without  mulching  the  trees 
with  litter.  The  grass  may  remain  without  cutting  or  it 
may  be  cut  and  removed  from  the  orchard  or  left  lying  on 
the  ground.  If  the  grass  or  litter  is  insufficient  at  least 
partially  to  kill  out  the  growth  beneath  the  trees,  it  must 
still  be  termed  sod  culture.  This  system,  like  all  the  fol- 
lowing, may  or  may  not  involve  the  use  of  manure  or  arti- 
ficial fertilizers  and  pasturing  with  stock.  The  grass  mulch 
system  consists  in  placing  a  mulch  of  litter  (grass,  straw, 
hay,  corn-stalks,  or  other  material)  beneath  the  trees,  usually 
extending  it  a  little  beyond  the  drip  of  the  branches.  As 
the  trees  become  large,  material  must  be  brought  in  from 
outside  the  orchard  in  order  properly  to  mulch  them.  A 
cleared  or  bare  area  should  be  maintained  immediately 
about  the  tree  trunks  as  a  fire  break  and  to  lessen  injury 
from  rodents.  Cleaii  tillage  involves  the  plowing  or  disking 
of  the  land  in  the  late  fall  or  spring  and  tilling  at  intervals 
of  about  two  weeks  throughout  the  early  summer,  usualty 
until  the  first  or  middle  of  July.  After  tillage  is  stopped, 
the  ground  lies  bare  until  the  following  spring,  hence  no 
vegetation  is  turned  into  the  soil.  The  tillage  and  cover-crops 
system  is  similar  to  the  former,  but  in  addition  to  the  tillage 
a  cover-crop  is  sown  at  the  time  of  the  last  cultivation  and 
the  crop  is  plowed  under  in  the  late  fall  or  spring.  Instead 
of  sowing  a  crop,  the  land  may  be  allowed  to  grow  up  to 
weeds.  Inter-cropping,  which  is  often  followed  in  young 
orchards,  refers  to  the  growing  of  any  crop  (usually  a  culti- 
vated one)  between  the  tree  rows  for  the  purpose  of  harvest- 


144  POMOLOGY 

ing  it  and  thus  utilizing  more  fully  the  land  not  yet  occupied 
by  the  trees.  The  system  of  alternate-row  cultivation  is  in  use 
in  some  regions  and  involves  the  tillage  and  perhaps  cropping 
of  every  other  "  land  "  or  area  between  alternate  rows  of  trees. 

126.  Sod  culture. — In  the  first  half  or  perhaps  three- 
quarters  of  the  nineteenth  century,  the  prevailing  prac- 
tice in  this  country  was  to  grow  fruit-trees  in  sod  land 
and  along  fence-rows;  especially  was  this  true  of  the  apple. 
This  was  before  the  western  orchard  sections  had  come  into 
existence  and  before  the  rise  of  commercial  orchard mg  in 
the  East.  In  the  last  quarter  of  the  past  century,  the  culti- 
vation of  orchards,  wherever  possible,  was  advocated  by 
the  progressive  growers.  Both  experiment  and  experience 
in  this  country  prove  that  sod  culture  is  the  poorest  way  of 
handling  an  orchard,  although  there  are  some  outstanding 
cases  to  the  contrary.^ 

The  chief  objection  to  the  sod  system  is  that,  on  the 
average,  fruit-trees  do  not  thrive  so  well  as  when  they  are 
at  least  partially  cultivated,  as  is  shown  by  the  growth  of 
trees,  color,  size,  and  amount  of  foliage,  and  yield  of  fruit. 
This  objection  may  be  entirely  or  partially  overcome,  how- 
ever, by  proper  fertilization  and  mulching  with  litter.  The 
reasons  for  these  effects  on  the  trees  are  discussed  later. 

On  the  other  hand,  certain  advantages  of  growing  trees 
in  grass  land  may  be  cited  as  follows: 

1.  It  prevents  the  >vashing  and  erosion  of  the  soil.  This 
is  not  so  true  in  New  England  and  other  northern  sections, 
because  the  ground  is  likely  to  be  frozen  during  the  so-called 
"soft  "  weather  in  winter  or  early  spring  that  occurs  farther 
south. 

1  The  student  should  not  confuse  sod  culture  and  grass  mulch,  for  they 
are  distinct  systems  if  properly  carried  out,  although  it  is  not  uncom- 
mon to  find  a  mulch  system  soon  degenerate  into  a  sod  culture,  and  thus 
they  may  be  confusing. 


CULTURAL  METHODS  IN  ORCHARDS  145 

2.  The  color  of  the  fruit  is  usually  higher  and,  therefore, 
it  has  greater  commercial  value  than  when  grown  under 
cultivation.  Not  all  varieties  are  affected  alike,  however, 
for  some  will  develop  a  high  color  under  tillage, 

3.  The  land  is  in  better  condition  for  spring  operations 
than  when  it  has  been  plowed.  This  applies  particularly 
to  heav}^  soils  which  do  not  drain  readily.  Also  there  may 
be  less  winter-mjury  in  the  sod  orchard, 

4.  The  dropped  fruit  is  of  higher  market  value. 

5.  Land  too  rocky  to  plow  or  to  permit  tillage  may  be 
ulitized  by  following  some  type  of  the  sod  system. 

6.  The  expense  of  caring  for  the  soil  is  reduced  to  little 
or  nothing,  in  some  cases  only  the  loss  of  the  land  for  pas- 
turage and  many  times  not  that, 

127.  Grass  mulch. — This  method  of  handling  an  orchard 
is  an  attempt  to  follow  nature  and  allow  litter  to  accumulate 
in  increasing  proportion  beneath  the  trees  and  thus  conserve 
moisture  and  add  plant-food  to  the  soil.  It  seems  to  have 
been  worked  out  simultaneously  by  F,  P,  Vergon  of  Delaware, 
Ohio,  and  Grant  Hitchings  of  Syracuse,  New  York.  Both 
of  their  orchards  are  commercially  successful  and  many 
have  emulated  the  practice. 

As  stated  in  the  definition,  the  mulch  system  is  limited 
to  the  practice  of  placing  sufficient  mulch  about  the  trees 
partially  or  entirely  to  kill  out  the  growth  of  grass  beneath 
them.  This  would  not  include  the  practice  of  mowing  the 
grass  of  the  orchard  and  letting  it  lie  where  it  falls,  although 
a  partial  mulch  is  thus  accumulated  after  a  few  years,  but 
the  grass  still  grows  beneath  the  trees  and  thus  the  evil 
effects  of  it  are  not  obviated.  This  latter  system  has 
been  termed  the  "sod  mulch"  to  distinguish  it  from  grass 
mulch. 

After  the  mulch  system  has  been  maintained  for  a  few 
years,  the  soil  beneath  the  mulch  becomes  loose  and  friable, 


146  POMOLOGY 

retains  moisture,  is  cooler  in  summer  and  freezes  less  in 
winter,  and  nitrates  may  be  more  abundant  than  when 
trees  are  grown  in  sod,  but  this  latter  is  not  always  true. 
The  growth  of  the  trees  is  usually  vigorous,  the  foliage 
abundant,  and  the  yield  much  improved  as  compared  with 
sod-grown  trees.  Under  most  conditions,  it  is  desirable  to 
add  artificial  fertilizers  or  animal  manures,  but  somethnes 
this  does  not  appear  necessary. 

It  is  usually  desirable  to  plow  the  land  before  setting  the 
trees.  It  may  then  be  seeded  down  and  the  mulch  system 
put  in  operation.  When  conditions  will  permit,  it  is  still 
better  to  cultivate  the  orchard  for  four  to  six  years.  How- 
ever, some  very  successful  orchards  have  been  planted  in 
grass  land  that  had  not  been  previously  plowed  for  a  nvunber 
of  years  and  no  ill  effects  appeared  after  the  system  had  been 
followed  for  a  long  period  of  time.  Its  success  under  such 
conditions  may  be  largely  attributed  to  an  abundant  supply 
of  moisture.  The  great  difficulty  is  that  neglect  may  result 
.and  the  orchard  soon  show  ill  effects,  as  indicated  by  sparser 
foliage,  smaller  and  yellowish  leaves,  and  small  fruits.  If 
faithfully  prosecuted,  however,  it  is  a  practical  system  of 
orchard  management,  and  well  adapted  to  many  conditions. 

On  hillsides  that  wash  badly  it  is  not  desirable  to  plow 
much  and  yet  the  sod  system  is  not  desirable;  hence  the 
mulch  finds  a  very  desirable  use.  The  same  may  be  said 
of  rocky  land.  Under  many  such  conditions,  it  is  not  a 
question  whether  grass  mulch  is  as  good  as  cultivation  but 
whether  it  is  better  than  nothing. 

The  mulch  system  is  perhaps  better  adapted  to  the  apple 
than  other  fruits,  although  the  pear,  quince,  and  small-fruits 
may  be  grown  in  this  way.  Under  few  conditions  should 
the  peach,  cherry,  or  plum  be  so  treated,  as  the  results  of 
tillage  methods  produce  much  better  results  and  longer-lived 
trees. 


CULTURAL  METHODS  IN  ORCHARDS  147 

Among  the  precautions  to  be  observed  with  mulched 
trees  are: 

1.  Protection  from  mice,  rabbits,  and  other  rodents.  The 
trees  should  be  safeguarded  by  either  a  mechanical  device 
or  by  means  of  a  protective  wash,  but  the  former  is  much 
more  reliable.  Rodents  are  more  likely  to  do  damage  in  a 
mulch  or  sod  orchard  than  in  a  cultivated  one  because  of  the 
harboring  places. 

2.  Fire  is  another  ever-present  danger  and  provision 
should  be  made  for  firebreaks  by  having  a  bare  space  between 
the  bole  of  the  tree  and  the  mulching  material.  On  a  young 
tree  this  area  should  be  about  a  foot  in  radius  and  as  the 
tree  becomes  older  it  should  gradually  be  increased  to  three 
feet.  A  mound  of  coal  cinders  about  the  tree  is  also  advis- 
able for  this  same  purpose. 

128.  Production  of  mulch  material. — One  of  the  problems 
in  a  large  grass  mulch  orchard  is  to  secure  sufficient  material 
for  mulching.  As  much  as  possible  is  secured  in  the  orchard, 
but  as  the  trees  become  older  the  amount  available  becomes 
less.  In  some  sections  oats  and  wheat  stubble  is  mowed 
about  two  or  three  weeks  following  the  cutting  of  the  grain 
and  in  this  way  a  large  amount  of  material  is  secured. 
Others  procure  hay,  straw,  or  the  like  for  the  purpose. 

One  of  the  striking  results  secured  by  the  Ohio  Experi- 
ment Station  ^  was  the  effect  of  fertilizers  on  the  increased 
growth  of  grass  in  the  orchard,  which  solved  the  mulch  prob- 
lem. It  was  found  that  when  acid  phosphate  was  used,  alone 
or  in  combination  with  potash,  a  striking  increase  in  growth 
of  the  clovers  resulted  without  any  seeding  whatever.  When 
nitrogen  was  used  alone  or  in  combination,  the  clovers  were 
crowded  out  by  the  timothy,  blue-grass,  red-top,  and  in 
some  cases  orchard-grass,  which  took  possession  of  the  land. 

iBallou,  F.  H.  Ohio  Agr.  Exp.  Sta.  Bull.  301.  1916.  Also  Bull 
339.    1920.    p.  16. 


.4 


148     ^5 


5^ 


POMOLOGY 


(^f^p^SJgSrVI.)     The  following  figures  show  the  results  ob- 
iea*m  one  orchard: 


1^»  Table  XXXII 

RESULTS  OF  FERTILIZERS  ON  YIELD  OF  MULCH   (AFTER  BALLOU) 


Annual  fertilizer  treatment  to  an  acre 

Yield 

Kind  of  grass 

Acid  phosphate,  350  lbs 

lbs. 
2,716 

2,884 

3,458 

840 

Acid  phosphate,  350  lbs. ;  muriate  of  potash, 
175  lbs 

Red  clover 

Acid  phosphate,  350  lbs. ;  muriate  of  potash, 
175  lbs. ;  nitrate  of  soda,  350  lbs 

Timothy,  red- 
top,  blue-grass, 
orchard-grass. 

Poverty-grass, 
weeds 

Unfertilized 

129.  Clean  cultivation  has  never  been  widely  used  in  the 
eastern  United  States,  but  in  sections  of  the  Northwest 
and  in  California  it  has  been  followed  extensively.  The 
danger  of  clean  tillage  seems  to  be  in  its  ultimate  effect  on 
the  soil  itself.  Especially  is  this  true  in  sections  in  which 
there  is  a  long  growing  season  and  the  summer  sun  is  intense.^ 
In  the  West  it  has  been  found  that  shade  or  cover-crops 
are  desirable  to  shade  the  ground,  thus  protecting  the  soil 
flora  and  also  maintaining  the  organic  matter  in  the  soil. 
While  this  system  may  and  often  does  give  satisfactory 
results  for  a  period  of  years,  it  is  likely  to  end  in  a  premature 
decline  of  the  trees  and  a  decrease  in  size  of  the  fruit.  This 
would  depend  on  the  climate,  the  nature  of  the  soil,  and  its 
fertility. 

130.  Tillage  and  cover-crop  system. — From  the  stand- 
point of  growth  and  yield  of  the  trees,  this  system  doubtless 

'  Paddock,  W.,  and  O.  B.  Whipple.  Fruit-Growing  in  Arid  Regions. 
New  York.    1910.    Ch.  11. 


CULTURAL  METHODS  IN  ORCHARDS  149 

stands  preeminent  for  most  orchard  lands  in  this  country. 
Except  for  economic  reasons  or  because  of  topography  of 
land  or  nature  of  its  surface,  it  would  usually  be  safe  to  follow 
this  practice.  While  the  chief  benefits  of  tillage  are  to  the  soil 
itself,  yet  certain  orchard  pests  are  better  controlled  when 
grass  or  weeds  do  not  occupy  the  land  between  the  trees. 
Rodents  and  some  of  the  injurious  diseases  and  insects  are  less 
prevalent  in  a  cultivated  orchard,  for  the  stirring  of  the 
ground  desti'oys  their  natural  harboring  places.  Weeds  like- 
wise are  kept  under  control,  avoiding  a  loss  of  soil-moisture 
and  plant -food  materials  to  the  trees.  Tillage  benefits  the 
soil  for  orchard  production  in  the  following  ways: 

1.  Maintains  a  better  medium  for  the  more  desirable 
soil    flora. 

2.  Increases  nitrification. 

3.  Makes  more  available  the  plant-food  materials  of 
the  soil. 

4.  Creates  and  preserves  a  surface  mulch  which  conserves 
moisture.^ 

131.  Cover-crops. — This  term  was  first  used  in  this  con- 
nection by  L.  H.  Bailey  in  1893  in  Bulletin  61  of  the  New 
York  (Coraell)  Experiment  Station.  It  has  its  origin  from 
the  fact  that  such  crops  are  planted  in  middle  or  late  sum- 
mer and  are  designed  to  make  a  cover  over  the  land  as  well 
as  a  winter  protection  and  to  recover  from  the  soil  surplus 
moisture,  as  well  as  readily  available  plant-food  materials 
and  thus  augment  the  maturity  of  the  trees;  also  to  pro- 
duce on  the  land  itself  a  green-manure  crop  for  main- 
taining fertility. 

The  value  of  cover-crops  in  an  orchard  has  been  ques- 
tioned by  some  authorities  on  the  grounds  that  no  special 
benefit  could  be  observed  where  they  had  been  used.    This 

1  See  also  Bailey,  L.  H.  Principles  of  Fruit-Growing.  20th  Ed. 
p.  76.    1915. 


150  POMOLOGY 

is  one  of  the  oldest  practices  in  agriculture  and  it  would  in- 
deed be  unfortunate  to  advocate  the  discontinuance  of  it 
unless  there  is  adequate  data  to  warrant  the  position.  This 
the  author  beUeves  is  not  the  case,  but  rather  that  in  the 
past  few  years  it  has  been  demonstrated  beyond  question 
that  the  practice  is  valuable  both  in  the  orchard  and  on  the 
farm.  To  test  the  soil  for  the  presence  of  organic  matter 
(carbon)  and  to  find  an  immaterial  gain  where  abundant 
organic  matter  has  been  returned  to  the  soil  for  a  long  pe- 
riod of  time  is  hardly  sufficient  evidence  on  which  to  rest  the 
case.  It  is  of  more  value  to  the  orchardist  to  know  that 
where  clean  tillage  has  been  followed  in  both  citrus  and  de- 
ciduous orchards,  the  soil  failed  properly  to  support  the  trees 
within  a  relatively  short  time.  When  cover-crops  were 
again  included  in  the  orchard  management,  the  trees  be- 
came vigorous  and  productive,  even  without  the  use  of  fer- 
tilizers. As  is  pointed  out  elsewhere,  the  hotter  the  climate 
and  the  longer  the  season,  the  quicker  will  the  humus  and  also- 
the  nitrogen  disappear  from  the  soil  through  tillage  methods. 
True,  there  may  not  be  sufficient  material  raised  to  main- 
tain an  increasing  ratio  of  organic  matter  as  the  trees  be- 
come mature  and  shade  a  large  portion  of  the  ground.  Then 
outside  material  may  be  resorted  to,  to  supplement  the  loss. 
Hence  the  present  teaching  must  be  that  abundant  cover- 
crops  are  the  safest  way  of  preventing  depletion  of  the  soil 
where  tillage  methods  are  followed. 

132.  Nitrification. — The  student  should  not  confuse  the 
two  groups  of  bacteria  that  have  to  do  with  the  nitrogen 
transformations  in  the  soil.  Where  legumes  are  grown, 
the  symbiotic  organisms  living  in  the  nodules  on  the  roots 
fix  nitrogen  of  the  soil-air  and  leave  it  behind  in  combined 
forms  in  their  remains  and  in  the  tissues  of  the  host.  Among 
the  organisms  concerned  in  the  decay  of  legumes  as  well  as 
of  other  plants  are  those  which  break  down  the  complex 


CULTURAL  METHODS  IN  ORCHARDS  151 

nitrogen  compounds  and  change  the  nitrogen  to  avaihible 
forms.  This  process  is  known  as  nitrification,  and  the  nitro- 
gen which  the  legume  organisms  took  from  the  air  is  not 
available  to  other  plants  until  these  nitrifying  organisms 
have  had  an  opportunity  to  do  their  work.  Incidentally 
it  should  be  mentioned  that  there  are  other  groups  of  ni- 
trogen-fixing organisms  in  the  soil  capable  of  taking  nitrogen 
from  the  soil-air  in  considerable  quantities   when  supplied 

Nitrogen  as  Nifrate 


Nitrogen  as 
/Immcm/a 

\__Nifragen  as 
1  Part  of  Plant 

Nitrogen  as  Organic  Matter 

Fig.  26. — A  graphic  representation  of  the  cycle  of  nitrogen  through 
the  plant  and  the  soil. 

with  an  abundance  of  phosphate,  limestone,  and  organic 
matter.  These  organisms  are  not  related  to  legumes  but 
are  present  in  all  normal  soils.  The  nitrogen  left  be- 
hind in  their  bodies  also  becomes  available  to  plants  in  the 
process  of  nitrification.  The  nitrification  process  is  graph- 
ically illustrated  in  Fig.  26. 

133.  Value  of  cover-crops  in  California.— In  semi-arid 
regions,  such  as  are  found  within  the  agricultural  section  of 
California,  there  is  a  notable  deficiency  in  the  organic  mat- 


152  POMOLOGY 

ter  of  the  soil,  and,  as  has  ah-eady  been  pointed  out,  where 
there  is  a  lack  of  organic  matter  there  is  also  likely  to  be  a 
lack  of  nitrogen.  Under  those  conditions,  legumes  proved 
to  be  far  superior  for  green-manures  as  evidenced  by  their 
effect  on  the  succeeding  crops.  The  yield  of  a  number 
of  crops  following  legume  green-manures  when  compared 
with  those  following  non-legumes  showed  the  following  in- 
creases: An  average  increase  with  potatoes  of  39  per  cent; 
with  com,  45;  with  cabbage,  44;  with  sugar-beets,  43  per 
cent,  respectively.  Legumes  alone  gave  as  good  or  better 
results  than  non-leguminous  green-manure  crops  plus  an 
annual  application  of  540  pounds  of  nitrate  of  soda  to 
the  acre. 

Of  more  direct  interest  in  this  connection  is  the  measur- 
able effect  of  green-manuring  on  citrus  fruit-trees.  The 
trees  on  plots  where  legumes  have  been  turned  in  annually 
were  superior  in  every  way  to  those  similarly  fertilized  but 
where  no  leguminous  green-manure  crops  had  been  used. 
Green-manuring  resulted  in  a  30  per  cent  increase  in  size 
of  tree  and  a  68  per  cent  increase  in  yield  at  the  age  of  ten 
years.  ^ 

134.  Effects  of  the  cultural  methods  on  the  soil. — Before 
examining  the  effect  of  these  cultural  systems  on  the  trees, 
it  would  be  well  to  follow  the  investigations  as  they  affect 
the  soil  itself.  While  the  student  must  consult  works  on 
soil  science  for  a  fuller  treatment  of  this  subject,  yet  some 
reference  to  it  is  necessary  in  order  to  secure  a  basis  for 
the  cultural  methods  used  in  orchards. 

It  is  axiomatic  that  an  abundance  of  available  inorganic 
plant-food  materials  and  moisture  will  give  a  better  devel- 
opment of  the  trees  and  production  of  fruit  than  when  these 
are  deficient  at  the  critical  period  of  development.  It  is, 
of  course,  equally  detrimental  to  have  excesses  of  moisture 
1  Mertz,  W.  M.    Calif.  Agr.  Exp.  Sta.  Bull.  292.    1918. 


CULTURAL  METHODS  L\  ORCHARDS  153 

and  in  some  instances  of  plant-food  materials,  and  this 
should  be  avoided. 

135.  Effect  of  moisture. — Hilgard,^  in  discussing  the 
effect  of  moisture  on  crop  production,  says:  "Production 
is  almost  directly  proportional  to  rainfall  during  the  period 
of  active  vegetation."  In  studying  the  moisture  relation, 
it  is  important  to  consider  the  type  of  soil.  A  clay  by  its 
nature  holds  more  moisture  than  a  light  soil,  so  that  when 
a  heavy  soil  contains  12  per  cent  of  moisture,  a  light  one 
under  the  same  conditions  may  only  have  about  7  to  9  per 
cent,  and  the  consequent  effect  on  the  trees  would  be  as  det- 
rimental under  the  one  as  under  the  other  condition,  be- 
cause of  the  factor  of  availability.  It  has  usually  been  ob- 
served that  the  soil-moisture  in  an  orchard  standing  in  sod 
is  less  than  when  the  soil  is  tilled,  but  under  some  condi- 
tions this  has  not  held  true. 

Woodbuiy  ^  shows  from  an  orchard  experiment  that 
moisture  was  less  under  sod  culture  than  under  tillage. 
"During  the  season  of  1913  and  1914  we  have  a  positive 
indication  of  the  effects  of  different  treatments  on  soil  mois- 
ture. In  both  of  these  seasons,  the  rain-fall  during  the  ac- 
tive growing  period  of  the  trees  (May,  June,  and  July)  was 
considerably  below  the  five-year  average  for  those  months. 
Inasmuch  as  the  cultural  practices  are  conservation  meas- 
ures, preventing  the  loss  of  water  after  it  enters  the  soil,  it 
is  largely  in  such  dry  periods  that  the  value  of  certain  sys- 
tems of  management  in  conserving  soil  moisture  are  made 
manifest. 

"In  both  of  these  years,  during  the  month  of  June,  the 
upland  plots  either  where  the  grass  was  cut  and  let  lie  or 
piled  under  the  trees,  were  low  in  soil  moisture.  Where  an 
adequate  mulch  was  maintained  on  the  surface  of  the  soil 

1  Soils,    p.  193. 

2  Purdue  Agr.  Exp.  Sta.  Bull.  205.    1917. 


154 


POMOLOGY 


either  through  the  agency  of  cultivation  or  by  a  heavy  straw 
covering,  the  percentage  of  moisture  was  more  than  twice 
that  in  straight  grass  land." 

Table  XXXIII 

MOISTURE   (total)  IN  SOIL   (AFTER  WOODBURY  ET  AL.) 


Straw 

Clean  culture 
cover-crop 

mulch, 
grass 
cut, 

Grass 

cut, 

let  lie 

Grass  cut, 
piled 

let  lie 

A 

B 

C 

D 

E 

F 

per  cent 

per  cent 

per  cent 

per  cent 

per  cent 

per  cent 

1913 

Apr.  29...  . 

18.9 

19.1 

19.2 

19.6 

18.5 

19.5 

June  17.  .  .  . 

14.6 

15.0 

18.8 

7.2 

6.1 

6.5 

Sept.    4 

14.0 

13.8 

15.6 

9.4 

9.4 

9.4 

Nov.  25 

20.4 

20.1 

21.3 

21.2 

20.3 

20.2 

1914 

May     6.... 

19.9 

19.8 

22.2 

21.6 

20.0 

21.0 

June  17..  .. 

15.3 

15.0 

17.6 

6.5 

6.1 

6.0 

Aug.  13...  . 

11.4 

10.4 

10.9 

7.2 

7.1 

7.9 

Nov.  25 

14.3 

14.7 

18.6 

16.1 

15.9 

17.3 

Data  obtained  at  the  New  York  State  Experiment  Sta- 
tion are  in  accord  with  those  cited  from  Indiana.  The  soil 
in  the  latter  experiment  is  described  as  follows:  "The  char- 
acter of  the  soil  changes  somewhat  with  the  topographical 
outlines  of  the  orchard.  On  the  ridge  and  high  ground  the 
soil  is  a  fertile  Dunkirk  sandy  loam  to  a  depth  of  nine  or 
ten  inches,  underlain  by  a  compact  sandy  subsoil.  In  the 
depression  the  type  changes  to  a  dark  colored  Dunkirk  loam, 
ten  to  twelve  inches  deep,  and  underlain  by  a  veiy  fine  com- 
pact  sand."  ^ 

1  N.  Y.  [GenevaJ  Agr.  Exp.  Sta.  Bull.  314.    1909. 


JI^R^ 

H 

Plate  IV. — Six-year  old  sour  cherry  trees,    o,  Unpruned;  h,  moderately 
pruned;  c,  heavily  pruned;  d,  summer  pruned. 


CULTURAL  METHODS  IN  ORCHARDS 


155 


It  is  concluded  from  an  experiment  in  the  above  orchard 
that,  "The  results  of  120  moisture  determinations  in  the 
Auchter  orcliard  show  that  the  differences  in  tree  growth 
and  crop  in  the  two  plots  of  this  experiment  are  mainly  due 
to  differences  in  moisture,  the  tilled  plot  having  most  mois- 
ture. As  a  consequence  of  the  reduced  water  supply  in  the 
sod  plot,  there  is  a  reduced  food  supply,  for  it  is  only  through 
the  medium  of  free  water  that  plants  can  take  in  food. 
Analyses  show  that  the  difference  between  the  actual  amount 
of  plant  food  in  the  two  plots  are  veiy  small." 


Table  XXXIV 

MOISTURE  TO  THE  ACRE  IN  TILLED  AND  SOD  PLOTS    (aFTER  HEDRICK) 


Soil,  depth 

Plot 

1907 

1908 

Amount  of  moist  are 

Amount  of  moisture 

1-6  in 

Tillage 
Sod 

Per  cent 
12.20 
7.30 

Per  cent 
14.04 
10.06 

1-12  in 

Difference 

Tillage 
Sod 

4.90 

11.53 

6.52 

3.98 

13.57 
9.37 

Diffprenrc 

5.01 

4.20 

Thus,  from  these  figures,  it  is  concluded  that  moisture 
is  the  limiting  factor  in  fruit  production  and  tree  growth  in 
this  orchard. 

On  the  other  hand,  the  New  Hampshire  Station  ^  de- 
scribes an  orchard  in  which  moisture  was  as  abundant  in  the 
sod  plot  as  in  the  adjoining  tilled  one,  and  hence  was  not 
1  N.  H.  Agr.  Exp.  Sta.  Tech.  BuU.  11.    1916. 


156 


POMOLOGY 


the  limiting  factor.  This  condition  is  not  the  usual  one, 
however,  although  the  same  conditions  obtained  in  southern 
Illinois.  The  average  difference  in  favor  of  the  sod  plot  is 
shown  below. 


Table  XXXV 

SUMMARY  OF  MOISTURE  DETERMINATIONS 
AVERAGE   TO    A   PLOT.      PERCENTAGE 

Surface  soil 

Y'ear 

Plot  1, 
sod 

Plot  4, 
tillage 

Plot  5, 
tillage  with  cover-crops 

1913 

1914                          .... 

16.02 

18.87 
25.63 
20.48 

13.69 
13.39 
19.29 
16.45 

14.20 
15.03 

1915              

20.82 

1916 

21.31 

Average 

20.25 

15.70 

17.84 

Subsoil 

1913 

1914 

1915 

10.98 
14.14 
14.26 
14.82 

9.06 
9.78 
14.03 
12.74 

8.93 
10.26 
13.33 

1916 

13.24 

Average 

13.55 

11.40 

11.44 

Much  the  same  results  were  obtained  at  the  Woburn  Ex- 
perimental Fruit  Farms  (England),  as  indicated  in  the  fol- 
lowing summary  of  the  data: 


CULTURAL  METHODS  IN  ORCHARDS 


157 


Table  XXXVI 

SUMMARY   OP   MOISTURE    DETERMINATIONS    (wOBURN) 
UPPER  9  INCHES 


Date 

Tilled  soil 

Grassed  soil 

Average 

Plot  13 

Plot  U 

Plot  IS 

Plot  IB 

Plot  16 

Plot  17 

diff. 

1907 
B.Aug.    7.. 
C.  Aug.  16.  . 
P.  Aug.  27 .  . 

13.50 
12.54 
11.30 

13.95 
12.54 
11.79 

12.13 
10.20 
11.40 

14.30 
10.00 
12.73 

14,86 

9.75 

11.43 

17.76 
12.15 
11.05 

+2.45 
—1,13 
+0.24 

Mean 

1910 
B.  Sept.  9 

1910 

Sept.  9. .  . 

12.45 

13.25 

Farmers 

A 

14.60 

12.76 
12.15 

12.60 
12.74 

Farmers 

B 

13.03 

13,82 

11.24 

12.38 

12.34 
14.07 

A 

19,70 

12.01 
12.67 

14.72 
14.84 

B 

13.72 
16.71 

13.54 
15.73 

+0.52 
+2.10 

+2,89 

136.  Effect  of  temperature. — The  temperature  of  the 
surface  soil  can  be  affected  somewhat  by  the  soil  treatment 
and  the  nature  of  the  soil  covering.  To  what  extent  a  few 
degrees  difference  in  temperature  may  affect  the  activity 
of  the  soil  flora  cannot  be  stated  definitely,  but  it  is  possible 
that  the  effects  are  greater  than  the  small  differences  of 
temperature  would  indicate.  Many  factors  are  involved 
in  affecting  the  soil  temperature,  but  the  greatest  are  the 
temperature  of  the  air  and  the  absorption  of  the  sun's  rays. 
(Fig.  27).  The  .work  of  Bouyoucos^  shows  that  a  difference  of 
as  much  as  five  degrees  of  temperature  may  obtain  between 
a  soil  which  is  tilled  and  one  which  lies  bare  or  is  in  sod. 
The  following  table  shows  the  data  as  a  monthly  average: 
1  Bouyoucos,  G.  J.    Mich.  Agr.  Exp.  Sta.  Tech.  Bull.  17.    1913. 


Fig.  27. — Curves    showing    the    maximum    soil    temperatur 
under  the  different  soil  treatments  in  an  orchard. 


CULTURAL  METHODS  IN  ORCHARDS 


159 


Table  XXXVII 

AVERAGE  MONTHLY  TEMPERATURE  OF  UNCULTIVATED,   CULTIVATED,   AND 
SOD    LAND.       (after  WOODBURY,    NOYES  AND   OSKAMP) 


7Ya7/(e  of 

Uncultivated 

Cultivated 

Sod 

month 

7" 

20" 

7" 

20" 

7" 

20" 

December 

January 

February 

March 

April 

34.5°F 
27.73 
30.73 
31.81 

42.24 

36.62°F 

34.84°F 
27.79 
29.42 
30.60 

39.63 
54.12 
64.4 
70.04 

66.24 
62.80 
50.46 
39.50 

35.94°F 
30.92 
30.06 
30.67 

37.10 
50.88 
60.64 
66.61 

63.75 
61.84 
50.90 
41.27 

34.38°F 
29.22 
30.07 
30.81 

41.93 

37.07°F 

May 

65.25 
71.09 

66.60 

63.48 
50.24 
39.77 

62.00 
66.94 

63.80 
61.90 
50.89 
41.20 

61.97 
65.55 

63.39 
59.60 

48.46 
39.85 

July 

64  0 

August 

September 

October 

November 

63.74 
61.40 
52.43 
45.07 

Orchard  experiments  confirm  these  figures  as  shown  by 
the  followmg   data: 

Table  XXXVIII 

SOIL  TEMPERATURE  IN  TILLED  AND  SODDED  LAND.      N.  Y.  STATE  EXP.  STA. 
DAILY JUNE  28  TO  JULY  29 


Depth  of  6  inches 

Depth  of  12  inches 

7  a.  in. 

6  p.  m. 

7  a.  m. 

6  p.  m. 

Sod 

Tilled 

Sod 

Tilled 

Sod 

Tilled 

Sod 

Tilled 

66.3 

67.4 

71. 

73.3 

64.5 

66.6 

65.4 

67.2 

This  work  has  been    repeated  in  orchards  under  the  va- 
rious systems  of  soil  management  with  much  the  same  re- 


160 


POMOLOGY 


suits.  In  one  orchard  ^  in  which  these  observations  were 
made,  it  was  found  that  the  soil  temperature  was  lowest  un- 
der the  heaviest  vegetation  and  highest  under  clean  tillage 
during  the  summer  and  the  reverse  in  winter;  also  the  heav- 
ier the  vegetation,  the  cooler  the  soil  during  the  summer 
and  the  warmer  in  the  winter.  The  following  figures  show 
the  effect  of  the  soil  treatment  during  the  growing  season: 

Table  XXXIX 

AVERAGE  SOIL  TEMPERATURE 
TILLED  AND  COVER-CROP  PLOTS  AT  8  INCHES.      N.  H.  EXP.  STA. 


Monthly  average,  April  to  September.    Records  made  at  2  p.  rn.  daily 


April .  .  . 
May.  .  . 
June. . . 
July.  .  . 
Aug .  .  .  . 
Sept . . . 
Average 


Sod 

Tilled 

38.3 

43.0 

52.3 

55.5 

59.3 

61.1 

66.8 

69.7 

66.6 

69.6 

61.9 

64.5 

57.5 

60.5 

42.5 
54.7 
57.9 
65.7 
65.2 
61.1 
57.8 


The  depth  of  freezing  in  these  same  plots  is  shown  at  a 
time  when  the  soil  was  supposedly  frozen  to  the  greatest 
depth  of  the  winter. 

Table  XL 


depth  of  freezing  IN  INCHES 

Sod 

Bare 
16 

Light 
cover- 
crop 

Heavier  cover-crops,  especially  in  last  three  plots 

Cover-crop 

Cover-crop 

Cover-crop 

Cover-crop 

Cover-crop 

12 

15 

12 

10 

8 

7 

7 

N.  H.  Agr.  Exp.  Sta.  Tech.  Bull.  12.     1917. 


CULTURAL  METHODS  IN  ORCHARDS 


161 


In  another  investigation  ^  it  was  found  that  the  "clean 
cultivation  with  cover-crop  and  the  straw  mulch  occupy 
the  extreme  positions  in  soil  temperature  behavior."  The 
bare  soil  will  respond  very  quickly  to  a  change  in  the  air 
temperature,  rising  rapidly  during  warm  weather  and  con- 
versely showing  the  lowest  temperature  in  the  winter.  By 
examining  Fig.  27  it  will  be  seen  how  closely  the  soil  temper- 
ature follows  that  of  the  air.     (Maximum  air  temperature.) 


,J 

^ 

^ 

V 

^ 

o. 

Z 

1 

O) 

<n3 

^ 

^ 

^ 

70 

^& 

,0^ 

/ 

\ 

M 

/^ 

.f 

\ 

SO 

/ 

\ 

40 

/ 

\ 

/. 

f 

\ 

30 

/ 

_\. 

ZO 

/ 



'"     ^ 

/.. 

^^- 

..       \ 

■^ 

sgo_ 



~       ■ 

Fig.  28. — Curves  showing  the  relative  formation  of  nitrates  under  sod, 
tillage,  and  tillage  cover-crop  systems  of  orcharding.  Parts  per 
million,  dry  soil. 

137.  Nitrates. — The  nitrogen  problem  is  of  paramount 
importance  in  discussing  the  fertility  of  an  orchard.  This 
is  because  in  many  cases  nitrogen  is  the  limiting  factor,  and 
also  because  it  is  a  very  expensive  element  to  purchase  in 
the  form  of  artificial  fertilizer.  Hence,  the  bacterial  activ- 
ities in  the  soil,  particularly  nitrification,  become  of  great  im- 
1  Ind.  Agr.  Exp.  Sta.  Bull.  205.     1917. 


162 


POMOLOGY 


portance  to  the  orchardist.  A  system  of  cultivation  which 
will  maintain  a  sufficient  supply  of  nitrates  and  produce  a 
good  growth  of  the  trees  together  with  high  yield  is  to  be 
sought.  The  effect  of  the  standard  cultural  methods  in  this 
regard  seems  to  be  marked.     (Fig.  28.) 

In  several  investigations  in  both  young  and  mature  or- 
chards, it  has  been  found  that  the  amount  of  nitrates  under 
sod  is  likely  to  be  very  low,  in  fact  so  low  as  to  be  the  lim- 
iting factor  in  production.  However,  Lyon  and  Bizzell 
have  shown  that  nitrification  is  not  depressed  when  leg- 
uminous crops  are  grown,  in  contrast  to  the  conditions  un- 
der rye  and  the  grasses.  When  the  soil  on  which  grass  has 
been  growing  is  stirred  by  cultivation,  the  nitrates  are 
greatly  increased,  especially  when  a  leguminous  crop  is 
plowed  into  the  soil  annually.  In  cases  in  which  the  moisture 
is  conserved  also,  the  results  of  cultivation  on  the  orchard 
are  likely  to  be  very  beneficial;  in  fact,  this  practice  is  usu- 
alty  one  of  the  first  steps  in  orchard  renovation. 

The  following  data  indicate  the  results  of  the  investiga- 
tions along  this  line: 

Table  XLI 

NITRATES  IN  LAUREL  SOIL  [PARTS  (NO3)  PER  MILLION  PARTS  SOIl] 

average  of  8  determinations  made  during  growing  seasons  op 
1914,  '15,  '16.     (adapted  from  woodbury  et  al.) 


Clean  culture 
cover-crop 
{2  plots) 

Straw  mulch 

grass  cut, 

let  lie 

Grass  cut, 
let  lie 

Grass  cut, 
piled  {3  plots) 

Hillside 

grass  cut, 

piled 

82  1 

53 

14 

17 

36 

Here,  as  in  the   experiments  that  follow,  it   was  found 
that  nitrates  were  reduced  under  grass  land  and  also  under 
rye  as  a  cover-crop.     The  highest  nitrates  were  present 
1  Seven  determinations  only. 


CULTURAL  METHODS  IN  ORCHARDS 


163 


where  the  system  of  tillage  and  cover-crops  was  practiced, 
and  the  straw  mulch  ranked  second  to  the  tillage  plots. 
While  not  indicated  in  the  data  in  the  above  table,  very- 
little  nitrate  was  found  in  late  fall  and  winter,  but  nitrifica- 
tion continued  later  in  the  fall  in  the  warmer  soil  under  the 
straw  mulch  than  elsewhere.  The  gains  made  by  the  trees 
in  this  experiment  were  roughly  proportional  to  the  nitrate- 
content  of  the  soil. 

The  New  Hampshire  Station  reports  the  same  results,  al- 
though the  averages  are  lower  in  all  cases.  The  averages  in- 
clude samples  taken  each  week  throughout  the  growing  sea- 
son for  the  four  years  and  this  may  account  at  least  in  part 
for  the  difference.  The  following  table  and  Fig.  28  epitomize 
this  work: 

Table  XLII 

summary  of  nitrate  determinations,  water  soluble  parts  to  the 

million  of  dry  soil 

Average  to  a  plot 

Surface  soil 


Year 

Plot  1, 
sod 

Plot  4, 
tillage 

Plot  5, 
tillage  mth  cover-crop 

1913 

2.64 
4.41 
2.09 
3.58 

18.25 
14.01 
21.05 
16.29 

38.37 

1914 

37.27 

1915 

18.75 

1916         

41.26 

Average 

3.18 

17.40 

33.91 

Subsoil 

1913 

1914 

1915         

1.55 
3.56 
1.51 
2.18 

6.90 
6.62 
10.76 
5.05 

6.87 
10.81 
6.88 

1916 

8.05 

Average 

2.20 

7.33 

8.15 

164  POMOLOGY 

It  is  further  stated  that  at  no  time  during  the  four  years 
in  which  the  investigation  was  in  progress  did  the  soil  sam- 
ples in  the  sod  plots  show  more  than  14.78  parts  nitrates 
per  million  of  dry  soil,  while  under  clean  tillage  they  were 
as  high  as  63  in  some  cases,  and  where  a  cover-crop  was 
plowed  in  they  occurred  as  high  as  132,  although  the  average 
for  the  plots  is  not  in  this  proportion. 

138.  Is  nitrification  retarded  under  sod? — Since  the 
grass  is  making  use  of  large  amounts  of  nitrates  in  a  sod  plot, 
it  is  but  reasonable  to  concede  that  the  quantity,  as  deter- 
mined by  analysis,  would  be  low,  although  nitrates  may  be 
formed  as  readily  there  as  when  the  soil  is  cultivated. 

In  order  to  arrive  at  some  conclusion  on  this  point,  ob- 
servations were  taken  on  the  sod  plot  in  the  above  experi- 
ment. A  small  plot  three  feet  square  was  selected  very  near 
to  the  point  where  the  soil  samples  had  been  taken  each 
year  previously  and  the  sod  was  carefully  removed  without 
stirring  the  soil  beneath.  Another  plot  of  equal  size  was 
selected  close  to  the  first  and  after  the  sod  was  removed  it 
was  spaded  to  the  depth  of  the  surface  soil  and  subsequently 
cultivated  with  a  hoe  weekly.  This  gave  three  conditions 
within  the  original  sod  plot:  (1)  sod;  (2)  bare  unshaded 
soil;  (3)  cultivated  soil.  While  the  bare  soil  would  not  rep- 
resent the  exact  conditions  under  sod,  yet  it  seems  to  be 
as  near  as  is  practical  to  obtain  in  the  field.  There  was 
practically  no  difference  in  soil-moisture  at  the  time  these 
observations  were  made.  The  results  would  seem  to  indi- 
cate that,  under  the  conditions  obtaining  in  this  experi- 
ment, nitrification  progressed  much  more  rapidly  under 
tillage  than  when  the  land  is  iii  sod  or  bare  and  uncul- 
tivated. 


CULTURAL  METHODS  IN  ORCHARDS 


165 


Table  XLIII 

nitrates,  parts  to  the  million  op  dry  soil 

surface  soil 


X' 

July 
SI 

Aug. 

7 

Aug. 
14 

21 

Aug. 

Sept. 

Sept. 
16 

Sept. 
£3 

.4  verage 
Aug.  7 

to 
Sept.  23 

Sod  .  . . 
Bare... 
Tilled.. 

2.599 
2.575 

1.871 
2.615 

2.800 
4.717 
10.575 

2.(3(),S 
3.330 
10.002 

3.748 
11.112 
24.969 

3.075 
10.755 
51.021 

4.27 
7.856 
65.553 

.568 
1.923 
8.332 

1.464 
2.380 
8.820 

2.6.56 
6.010 
26.469 

These  results  are  not  in  accord  with  the  findings  of  some 
writers  ^  who  state  that  neither  moisture  nor  nitrates  are 
influenced  by  cultivation.  The  chief  reason  given  for  loss 
of  moisture  and  nitrates  is  the  weeds  that  utilize  them, 
and  if  the  weeds  are  removed,  it  is  contended,  the  nitrates 
will  be  found  as  abundantly  with  no  tillage  as  with  it. 
An  explanation  of  these  observations  in  regard  to  mois- 
ture is  suggested  by  Lyon  -  as  follows:  "It  seems  possible 
that  the  latter  result  may  occur  only  in  those  regions  in 
which  conditions  are  such  that  a  natural  mulch  is  formed 
by  a  rapid  diying  of  the  surface  soil  in  which  process  mois- 
ture is  removed  so  rapidly  that  the  capillary  colmim  is 
broken  and  further  loss  of  moisture  is  stopped.  This  would 
confine  it  to  semi-arid  and  arid  regions  of  high  summer 
temperatures." 

139.  The  toxic  theory. — It  is  accepted  at  the  present 
time  that  toxic  substances  are  found  in  certain  soils,  i.  e., 
compounds  poisonous  to  certain  plants.  Lack  of  soil  aera- 
tion, proper  "sanitary"  conditions,  or  poor  drainage  seems 
to  explain  their  existence.  Some  writers  hold  that  the  whole 
problem  of  soil  fertihty  is  largely  one  of  toxicity,  and  that 
the  application  of  the  various  fertilizers  merely  results  in 
neutralizing  the  toxic  effect.     This  theory  has  been  used 

iCall,  L.  E.,  and  M.  C.  Sewell.  Jour.  Amer.  Soc.  Agron.  Vol.  10, 
No.  1,  Jan.,  1918. 

2  Lyon,  T.  L.    Soils  and  Fertilizers.    Rural  Text-Book  Series. 


166  POMOLOGY 

by  some  to  explain  the  cause  of  trees  doing  poorly  in  sod 
and,  conversely,  why  they  thrive  when  the  soil  is  cultivated. 
The  work  of  Bedford  and  Pickering  along  Lhis  line  is  dis- 
cussed later  in  the  chapter. 

140.  Effect  of  cultural  systems  on  the  growth  of  the  trees. 
— (For  convenience  of  study  and  to  avoid  complications, 
the  data  are  given  from  unfertilized  orchards  only.)  The 
results  of  an  experiment  to  determine  the  effects  of  tillage 
and  sod  mulch  in  a  Baldwin  apple  orchard  have  been  re- 
ported by  Hedrick.^  The  experiment  was  continued  for 
ten  years  and  the  trees  were  twenty-six  years  old  at  the  be- 
ginning. While  the  type  of  mulching  given  these  trees  would 
not  agree  with  our  definition,  yet  more  than  two  tons  of 
grass  to  the  acre  were  allowed  to  remain,  thus  giving  more 
mulching  material  than  is  ordinarily  used  when  placed  be- 
neath the  trees.  The  results  are  very  striking,  as  they  show 
that  the  tilled  trees  made  much  greater  diameter  growth 
than  those  not  tilled. 

Table  XLIV 


GAIN  IN 

DIAMETER  OF  TREE  TRUNKS  ON  SOE 
(after  HEDRICK.) 

AND  TILLAGE  PLOTS 

Sod  {average  61  trees), 
inches 

Tilled  {average  60  trees), 
inches 

1913          

16.08 
13.70 

2.38 

17.15 

1903        

13.25 

3.90 

It  is  further  recorded  that  the  sodded  trees  showed  infe- 
riority in  all  respects  when  compared  with  the  tilled  ones. 

Such  results  as  these  are  very  common  in  orchards  grow- 
ing in  sod  alone  and  the  sparse  yellowish  foliage  is  familiar 
to  all  observers.  However,  when  mulching  material  is  added 
in  sufficient  amounts  (about  50  to  100  pounds  diy  matter 
1  N.  Y.  (Geneva).  Agr.  Exp.  Sta.     Bull.  314  and  383. 


CULTURAL  METHODS  IN  ORCHARDS 


167 


to  a  tree  annually),  the  trees  often  show  considerable  gain, 
and  when  nitrate  of  soda  is  also  used  the  orchard  will  not 
infrequently  do  as  well  as  when  tilled.  It  then  becomes 
largely  a  question  of  soil  and  amount  of  available  moisture 
during  the  critical  season  of  growth. 

Woodbury  and  associates  report  that  "Trees  grown  un- 
der a  clean  culture  cover-crop  system  or  under  a  heavy  mulch 
made  44.5  per  cent  greater  average  yearly  gains  in  trunk 
girth  than  trees  grown  in  grass  with  a  light  mulch  or  no  mulch 
at  all.  There  has  been  no  significant  difference  between  the 
three  varieties  in  their  response  to  soil  management  treat- 
ments. The  Stayman  variety  made  slightly  greater  gains  in 
girth  of  trunk  on  all  plots  than  did  Grimes  or  Jonathan." 

In  support  of  this  conclusion,  the  following  data  are  sub- 
mitted : 

Table  XLV 
detailed  growth  record  of  permanent  trees  for  five-year  period 

(after  WOODBURY  ET  AL.) 


Plot 

Number 
trees  in- 
cluded in 
averages 

.4; 

erage  girth 

Year- 

Systems of 
management 

1.916 
cm. 

1011 
cm. 

1912- 
1916 
cm. 

ly 
gain 
cm. 

Clean  culture  cover- 

A 
B 

90 
62 

33.88 
32.68 

8.02 
7.54 

25.86 
25.14 

5  17 

5.03 

Straw  mulch 

grass  cut,  let  lie .  . 
Grass  cut,  let  lie. . .  . 

I 

61 

84 

33.24 
24,32 

7.30 
7.17 

25.94 
17.15 

5.19 
3.43 

Grass  cut,  piled .... 

E 
F 

47 
79 

26.00 
25.31 

7.90 
7.25 

18.10 
18.06 

3.62 
3.61 

Hillside 

grass  cut,  piled. .  . 

0 
H 

53 

89 

28.93 
30.71 

15.15' 
8.41 

13.78  2 
22.30 

4.. 59 
4.46 

1  Girth.  1913. 


Gain  in  girth,  1914  to  1916. 


168  POMOLOGY 

They  also  report  that,  "The  terminal  twig  growth  has 
been  measured  and  found  to  correlate  satisfactorily  with 
girth  increase." 

At  the  Pennsylvania  Experiment  Station,  a  series  of  cul- 
tural experiments  was  conducted  in  various  parts  of  the 
state,  thus  including  various  soil  types.  Table  XLVI  gives 
the  results  of  the  treatment  on  the  growth  of  the  trees  only, 
as  the  effect  on  the  yield  is  considered  later.  In  two  cases 
the  sod  mulch  system  gave  decidedly  the  best  results  in 
growth,  with  tillage  and  cover-crops  ranking  second,  tillage 
(clean  cultivation)  third,  and  sod  poorest.  In  the  other 
ten,  the  order  of  the  first  two  is  reversed  and  tillage  and 
cover-crops  gave  the  best  results  by  a  very  decided  margin.  It 
seems  that  the  younger  trees  respond  best  to  the  mulch  sys- 
tem and  the  older  ones  to  tillage  methods,  while  sod  gives 
poor  results  on  all  trees. 

The  New  Hampshire  experiments  again  show  the  superi- 
ority of  tillage  over  sod.  After  ten  years'  work  in  renovat- 
ing a  declining  Baldwin  orchard,  it  was  found  that  the 
trees  growing  in  sod  made  such  inferior  growth  most  sea- 
sons as  to  make  them  less  able  to  withstand  the  destructive 
influences  of  weather  and  parasites.  On  the  other  hand, 
tillage  every  other  year  resulted  in  a  decided  benefit  to  the 
trees,  but  better  results  were  obtained  when  tillage  was 
followed  annually,  amounting  to  43  per  cent  greater  than 
when  trees  were  grown  in  sod.  However,  the  results  of  this 
work  are  significant  as  they  point  to  the  conclusion  that  this 
system  (clean  culture)  could  not  be  continued  over  a  long 
period  of  time  on  the  soil  involved,  since  at  the  end  of  ten 
years  the  trees  were  not  making  so  good  an  average  growth 
as  at  the  end  of  the  first  five-year  period,  which  is  inter- 
preted as  a  decline. 

When  cover-crops  were  plowed  in  annually,  there  was  an 
additional  18  per  cent  increase  in  growth.     However,  under 


CULTURAL  METHODS  IN  ORCHARDS 


169 


Table  XLVI 

influence  of  cultural  treatments  on  the  growth  of  trees 

average  gain  in  trunk-girth  to  a  tree.   no  fertilizers  or  manures 

USED.l       (after  STEWART) 


Varieties 

1* 

1 
40 

Tillage  and 
cover-crops, 
inches 

1-^ 

2 
1 

Jonathan 
York,  Gano. .  .  . 
Ben  Davis 

1902 

1907-1915 

14.39 

14.46 

15.64 

12.32 

York 

Yellow  Newton 

1900 

1893 

1907-1915 

40 

40 

40 

13.52 

16.07 

16.87 

13.36 

Smokehouse, 
Stayman 

1901 

1908-1915 

20.03 

17.50 

13.92 

Baldwin, 

Northern  Spy. . 

1873 

1907-1915 

9.09 

6.46 

the  conditions  obtaining  in  this  experiment,  the  growth  was 
not  being  maintained  by  this  treatment,  as  is  shown  by  the 
data  at  the  end  of  the  first  and  second  five-year  periods.  On 
stronger  soils,  the  time  would  be  delayed  when  such  a  de- 
cline would  begin  to  be  evident.  When  fertilizers  were 
added,  both  the  cover-crop  and  trees  showed  the  growth 
to  be  in  an  increasing  ratio  rather  than  in  a  decreasing  one. 
This  means  that  tillage  with  cover-crops  is  somewhat  su- 
perior to  tillage  alone,  but  a  lighter  soil  will  show  the  lack 
of  green-manuring  before  a  stronger  one,  the  length  of  time 
depending  on  the  original  fertility  of  the  soil. 

1  Pcnn.  Agr.  Exp.  Sta.  Bull.  141.      1916. 


170 


POMOLOGY 


Table  XLVII 

average  annual  twig  growth  to  a  tree  in  inches 


Sod 

Tilled  in 
alternate  years 

Clean  tillage 

Tillage  and 
cover-crops 

Plot 

1 

Plot 

2                3 

Plot 

4 

Plot 

5 

10-yr.  ave 

5.09 

5.41 

6.82 

7.31 

8.21 

Percentage 
increase 
over  plot  1 .  . 

6 

34 

43 

61 

141.  Leaf  area. — In  all  these  experiments  the  foliage  is 
a  notable  index  to  the  vigorous  condition  of  the  trees  or 
the  reverse,  both  in  the  abundance  of  leaves  and  in  their 
size  and  color.  As  an  illustration,  the  following  figures  may 
be  cited: 

Table  XLVIII 
effect  of  cultural  methods  on  leaf  size 

Average  area  of  leaves 
in  square  inches 

Trees  in  sod 4 .  24 

Clean  tillage 5 .07 

Tillage-cover-crops 5 .  28 

Not  only  are  the  area  and  abundance  of  the  leaves  reduced 
under  sod  culture,  but  the  foliage  often  turns  yellow  and 
drops  prematurely.  A  cross-section  of  such  leaves  shows 
that  there  is  one  layer  of  palisade  cells  and  another  layer 
about  half  the  length  of  the  surface  or  first  layer.  In  con- 
trast with  this  structure,  the  leaves  on  trees  in  a  high  state 
of  vigor  show  three  and  sometimes  a  partial  fourth  layer  of 
palisade  cells  and  a  denser  structure  of  the  mesophyll. 


CULTURAL  METHODS  IN  ORCHARDS 


171 


142.  The  Woburn  experiments.^ — The  work  of  the 
Wobum  Experimental  Fruit  Station  on  the  effect  of  sod  on 
the  growth  of  trees  is  of  special  interest,  since  it  is  viewed 
from  the  standpoint  of  the  toxicity  of  the  soil.  The  results 
there  are  not  paralleled  in  this  country  so  far  as  the  extreme 
effect  of  sod  on  trees  is  concerned.  It  was  found  that  young 
orchards  planted  in  sod  made  a  feeble  growth  and  soon 
reached  the  point  of  death  if  not  tilled.  No  form  of  ill- 
treatment  would  produce  such  enfeebling  results  with  the 
exception  of  transplanting  the  trees  each  year.  Not  only 
did  trees  planted  in  sod  show  this  effect,  but  those  which 
had  made  a  vigorous  growth  in  tilled  land  for  a  period  of 
four  years  showed  the  ill  effects  at  once  when  the  land  was 
laid  down  to  grass.  Within  five  years  most  of  the  trees  of 
the  weaker  varieties  were  entirely  dead.  The  work  was 
repeated  under  vaiying  conditions,  with  different  varieties 
and  with  both  standard  and  dwarf  kinds.  Some  vari- 
eties proved  resistant  to  the  effect  of  the  grass,  but  mostly 
they  suffered  extensively.  Different  kinds  of  fruits  varied 
in  their  behavior  toward  the  sod  as  is  seen  by  the  following 
data: 

Table  XLIX 
values  compared  with  ungrassed  trees  =  100 

(after  BEDFORD  AND  PICKERING) 


Leaf-size 

Prunings 

Crops 

Cherries 

Pears 

88 
72 
72 
68 

32 
21 

7 
- 

8 
0 

1  5 

Apples 

6 

When  grassed  trees  in  low  vitality  were  again  tilled,  they 
made  an  immediate  response  to  the  culture.    (This  was  also 
the  experience  of  Hedrick  in  the  Auchter  orchard.)     Con- 
1  Woburn  Exp.  Fruit  Farm  Kept.,  1,  2,  3,  13,  14. 


172 


POMOLOGY 


versely,  when  tilled  trees  were  gradually  grassed  over,  they 
showed  the  deleterious  effect  so  common  to  this  fonn  of 
treatment.  In  one  block  of  standard  apples,  the  sod  was 
replaced  immediately  after  planting,  and  when  they  were 
compared  with  a  block  of  similar  trees  under  tillage  but 
which  were  gradually  allowed  to  grass  over,  the  following 
significant  results  were  obtained: 

Table  L 
annual  growth  op  tilled  trees  =  100 


(after  BEDFORD 

AND   PICKERING) 

1910 

1911 

191;^ 

1913 

1914 

1915 

Mean 
1911-15 

Turf  replaced 

Grassed  gradually. .  .  . 

76 
101 

30 

38 

6 
12 

5 
10 

11 
33 

7 
28 

12 
24 

These  results  are  explained  entirely  on  the  ground  that 
some  toxic  influence  is  interfering  with  the  normal  func- 
tioning of  the  plant  and  preventing  it  from  utilizing  the  food 
present.  Somewhat  similar  results  in  this  country  have 
been  explained  largely  by  the  low  rate  of  nitrification  and 
often  the  reduction  in  soil-moisture,  but  toxic  substances, 
perhaps  due  to  lack  of  oxidation,  may  be  involved  in  the 
low  nitrification  which  occurs. 

In  general,  these  various  experiments  would  seem  to  bear 
out  fully  the  results  that  might  be  anticipated  from  a  study 
of  the  effects  of  culture  on  the  soil.  Sod  has  practically 
always  inhibited  the  growth,  size,  color,  and  amount  of  fo- 
liage on  the  trees.  Toxicity  and  lack  of  available  nitrogen 
and  moisture  may  all  play  important  parts  in  the  effects 
secured.  Tillage  has  universally  increased  growth  and  gen- 
eral vigor  of  the  trees  and  the  same  is  often  true  when  a 
mulch  of  litter  is  placed  about  the  trees  to  such  a  depth  as 
will  destroy  the  growth  of  grass.     Even  partial  tillage  or 


CULTURAL  METHODS  IN  ORCHARDS  173 

only  one  cultivation  for  the  season  will  produce  markedly 
increased  results  as  compared  with  sod. 

143.  Yield  of  fruit. — As  previously  stated,  the  soil  treat- 
ment is  larg(>ly  responsible  for  the  amount  of  bloom  and 
hence  for  the  possibilities  of  a  crop  of  fruit.  Therefore,  it 
becomes  of  the  first  importance  to  study  the  cultural  treat- 
ments that  are  most  likely  to  give  a  maximum  crop,  so 
long  as  this  is  not  inconsistent  with  the  health  and  vigor  of 
the  trees. 

A  fundamental  principle  established  by  all  the  experi- 
mental evidence  at  hand  may  be  stated  as  follows:  The 
growth  of  the  tree  and  yield  of  fruit  proceed  in  the  same  di- 
rection and  are  not  antagonistic.  This  of  course  is  within 
reasonable  limits,  for  a  point  may  be  reached  when  the 
growth  is  so  excessive  as  to  suppress  flower-bud  fonnation. 
An  extreme  of  such  a  condition  is  reported  from  the  tropics.^ 
"Of  our  apple  trees  it  is  well  known  that  in  warm  insular 
climates  they  grow  into  magnificent  foliage  trees,  but  re- 
main unproductive." 

In  keeping  with  this  principle,  it  may  be  said  that  the 
above  data  on  the  growth  of  the  trees  applies  with  much 
the  same  force  to  the  yield.  In  regard  to  jneld  no  one  sys- 
tem is  always  best,  but  the  one  most  suitable  to  the  condi- 
tions should  be  adopted. 

As  seen  above,  the  purposes  of  adopting  a  cultural  sys- 
tem are  to  conserve  sufficient  moisture  for  maximum  re- 
sults, to  increase  nitrification  in  the  soil,  and  to  set  free  plant- 
food  materials,  as  well  as  to  control  weed  growth.  This, 
interpreted  in  terms  of  the  plant,  results  in  increased  growth 
and  fruitfulness. 

144.  Sod,  tillage,  and  mulch  for  the  apple. — The  work 
with  the  apple  shows  that,  as  a  rule,  the  trees  growing  in  sod 
land  are  lower  in  yield  and  the  fruit  smaller  but  higher  in 

'  Sorauer,  P.    A  Treatise  on  Physiology  of  Plants,     p.  222. 


174  POMOLOGY 

color  than  when  cultivated.  If  the  trees  are  in  sod  mulch,  the 
yield  is  somewhat  higher  than  in  sod  alone,  although  as  a  rule 
fertilizers  or  manures  are  necessary  to  obtain  best  results. 

Some  of  the  best-known  experiments  in  this  country  have 
been  conducted  by  the  New  York  Experiment  Station  and 
have  been  referred  to  in  the  discussion  of  "growth."  To 
recapitulate  and  state  in  more  detail:  The  experiment  was 
conducted  as  follows  (Auchter  orchard).  The  soil  was  a 
fertile  Dunkirk  loam,  about  ten  inches  in  depth  and  under- 
laid by  a  sandy  subsoil.  The  orchard  of  nine  and  one-half 
acres  of  Baldwin  trees  was  divided  in  half  in  the  first  five 
years,  so  that  118  were  left  in  sod  and  121  under  tillage.  In 
the  second  five-year  period,  the  orchard  was  divided  into 
quarters  so  that  one  quarter  was  in  sod  for  ten  years  and 
another  in  tillage  for  ten  years,  a  third  quarter  was  in  sod 
for  five  years  and  under  tillage  the  latter  five  years,  while 
the  other  fourth  was  in  tillage  the  first  five  years  and  in  sod 
five  years.  While  potash  and  phosphoric  acid  were  used 
for  the  first  three  years  in  this  experiment,  no  results  were 
noted  where  they  were  applied  and  this  fact  need  not  come 
into  the  present  discussion. 

The  plot  which  was  tilled  for  ten  consecutive  years  re- 
sulted in  an  average  yield  to  a  tree  of  4.29  barrels;  the  plot 
in  sod  for  ten  years  yielded  2.54  barrels  to  the  tree;  the  plot 
which  was  tilled  for  five  years  and  in  sod  five  years  averaged 
for  the  second  five-year  period  2  barrels  to  the  tree;  while  the 
plot  which  was  first  in  sod  for  five  years  and  then  tilled  for 
five,  gave  an  average  of  5.17  barrels  during  the  second  period. 
These  figures  are  very  striking  and  emphasize  the  value  of 
tillage  under  the  conditions  of  this  orchard. 

Another  experiment  by  the  New  York  Experiment  Sta- 
tion was  conducted  for  a  ten-year  period  to  determine  the 
value  of  tillage  and  mulch  in  an  apple  orchard  (Hitchings 
orchard).     In  this  case,  the  land  was  deep,  fertile,  and  well 


CULTURAL  METHODS  L\  ORCHARDS 


175 


supplied  with  moisture,  which  factors  favor  the  mulch  sys- 
tem of  orcharding.  At  the  end  of  the  period,  the  four  vari- 
eties (Alexander,  Fameuse,  Northern  Spy,  and  Wealthy) 
averaged  3.18  bushels  of  apples  to  the  tree  on  the  tillage 
block  and  3.95  bushels  on  the  sod  mulch  plot. 

The  Pemisylvania  experiments  show  the  same  general 
results  in  yield  as  in  growth.  The  statement  of  Stewart  is 
that  "In  general  the  mulch  treatment,  reinforced  by  out- 
side materials,  has  been  most  efficient  in  improving  the 
yield,  growth,  and  average  size  of  fruit  in  orchards  up  to 
about  20  years  of  age.  In  older  orchards,  it  has  been  sur- 
passed slightly  by  tillage  and  cover-crops,  unless  accom- 
jianied  by  adequate  fertilization.  It  has  also  been  most 
efficient  in  conserving  moisture,  in  all  cases  that  have  been 
determined." 

Table  LI 

INFLUENCE  OF  CULTURAL  TREATMENTS  ON  THE  YIELD  OF  TREES 
AVERAGE   ANNUAL   YIELD  TO  THE   ACRE       (aFTER  STEWART) 


Varielies 

^1 
It 

i 

i! 

1 

'^    a. 

II 

1 

1 

Jonathan 
York,  Gano, 
Ben  Davis 

1902 

1907-1915 

40 

Bu. 

78.4 

Bu. 

85.7 

Bu. 
152.6 

Bu. 

78.1 

Smokehouse, 
StajTiian 

1901 

1908-1915 

40 

127.9 

147.5 

43.7 

Baldwin, 
Northern  Spy 

1873 

1907-1915 

40 

398.0 

385.2 

The  New  Hampshire  experiments  show  again  the  value 
of  tillage  over  sod  culture  of  the  trees.     The  conclusions 


176  POMOLOGY 

from  the  work  are  as  follows:  The  trees  growing  in  sod 
have  not  yielded  sufficiently  well  to  warrant  the  use  of  the 
land  for  orcharding.  Tillage  every  other  year  resulted  in 
decided  benefit  to  the  trees.  Clean  cultivation,  without 
the  use  of  green-crops,  has  proved  successful  in  the  recla- 
mation of  a  run-down  orchard,  increasing  the  yield  nearly  100 
per  cent.  It  has  shown  evidence,  however,  that  it  could 
not  be  continued  for  a  long  period  of  time  as  the  trees  were 
not  quite  so  vigorous  at  the  end  of  a  ten-year  period  as  at 
the  completion  of  the  first  five  years.  Tillage  with  cover- 
crops  has  proved  to  be  a  slightly  better  system  than  clean 
tillage  alone.    For  yields  of  these  plots  see  page  206. 

145.  Cultivation  for  the  peach. — What  has  been  said 
in  regard  to  tillage  applies  with  particular  force  to  the  peach. 
In  fact,  it  is  doubtful  whether  the  peach  will  ever  do  as  well 
under  any  other  system  as  under  cultivation.  Most  soil 
experiments  with  this  fruit  include  fertilizers  and  are  hence 
treated  in  the  next  chapter.  Ralston  ^  cites  some  work 
however,  confirming  the  value  of  tillage  for  the  peach.  There 
were  288  trees  to  the  plot  equally  divided  between  Early 
Crawford  and  Elberta.  The  trees  were  planted  in  1 9 1 1  and  the 
data  taken  1915-17,  inclusive.  The  soil  is  described  as  a 
''very  poor  Cecil  Clay  which  contains  an  abundance  of  small 
pebbles  and  a  small  amount  of  loose  shale,  and  is  fairly  uni- 
form throughout." 

Table  LII 
results  of  cultural  treatments 

YIELD  OF  FRUIT  IN  POUNDS  TO  A  TREE  FOR  3  YEARS.     (AFTER  RALSTON) 


Intense  cultivation 
(7  to  9  times  annually) 

Commercial  cultivation 
{3  to  4  times  annually) 

Sod  {in  sod  since 
spring  of  1913) 

1,943  lbs. 

1,285  lbs. 

712  lbs. 

Ralston,  G.  S.    23d  Ann.  Kept.  Va.  Hort.  See.    1918. 


CULTURAL  METHODS  LY  ORCHARDS  177 

146.  Fall  plowing  the  orchard. — If  the  orchard  can  be 
safely  plowed  in  the  fall,  it  will  result  in  a  saving  of  time  in 
the  spring  when  a  great  demand  exists  for  teams  and  men. 
This  practice  has  been  put  to  the  test  in  many  of  the  fruit- 
growing regions  and  without  resultant  injuiy  to  the  trees. 
Fall  plowing  can  be  followed  in  both  the  North  and  South, 
and  with  tender  fruits  such  as  the  peach  as  well  as  with  the 
apple  provided  the  soil  will  not  erode.  The  land  is  usually 
allowed  to  lie  in  the  rough  (without  harrowing)  over  winter 
and  is  harrow(Hl  down  in  the  spring. 

147.  Use  of  explosives  for  tillage  purposes.^ — Much  has 
recently  been  written  in  regard  to  the  use  of  explosives  in 
the  planting  of  young  trees  and  also  in  the  tillage  of  mature 
ones.  The  experimental  work  on  this  subject  is  not  exten- 
sive, although  these  agencies  have  been  extensively  used 
both  as  demonstrations  and  in  conmiercial  work. 

That  a  well-developed,  extensive  root  system  is  correlated 
with  a  vigorous  productive  top  of  a  fruit-tree  goes  without 
saying,  and  the  theory  of  the  use  of  explosives  for  this  pur- 
pose is  well  founded.  Whether  such  extraordinaiy  means 
are  necessaiy  will  depend  on  the  nature  of  the  soil,  for  if  it 
is  hard  and  impervious,  rocky  or  underlaid  with  hard-pan 
or  other  resistant  material,  the  use  of  an  explosive  should 
be  most  helpful.  There  is,  however,  no  virtue  in  the  use  of 
dynamite  other  than  what  is  gained  by  a  better  mechanical 
soil  condition,  or  else  in  the  cost  of  the  operation.  The  soil 
should  not  be  wet  at  the  time  of  the  operation  or  a  pot-hole 
is  likely  to  be  blown  out  which  makes  a  basin  for  water  and 
is  hence  more  harmful  than  other  methods.  It  is  usually 
advisable  to  blow  the  holes  some  time  before  setting  in  order 
to  allow  the  soil  to  settle;  othei-wise,  the  trees  are  likely  to 
sink  a  few  inches  which  is  quite  undesirable. 

>  "The  Use  of  Explosives  in  the  Tillage  of  Trees."  Pub.  by  Institute  of 
Makers  of  Explosives,  New  York.     1918. 


178  POMOLOGY 

Farley  ^  conducted  some  experiments  with  peaches  in 
which  he  fomid  that  there  was  usually  an  increase  in  growth 
of  the  trees  during  the  first  summer  when  they  were  planted 
with  dynamite  as  compared  with  trees  set  in  the  usual  way. 
In  one  experiment  this  increase  was  not  maintained  during 
the  second  and  third  season.  "The  crop  of  peaches  pro- 
duced by  the  New  Brunswick  and  Vineland  trees  during 
the  third  summer  show  a  noticeable  advantage  in  favor  of 
dynamiting  in  the  case  of  the  variety  Carman,  the  only 
variety  which  produced  what  could  be  termed  a  profitable 
crop." 

In  general,  however,  he  concludes,  that,  "The  results  of 
our  experiments  indicate  that  in  the  majority  of  cases  the 
increased  growth  and  fruit  production  recorded  on  dyna- 
mited trees  is  not  great  enough  to  make  up  for  the  increased 
cost  and  danger  involved  in  planting.  Furthermore,  the 
use  of  dynamite  is  not  recommended  for  tree  planting  on 
those  soils  that  are  naturally  adapted  to  orcharding." 

1  Farley,  A.  J.    Proc.  Amer.  Soc.  Hort.  Sci.    1914. 


CHAPTER  IX 
FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD 

The  supplying  of  artificial  plant-food  materials  to  fruit- 
trees  introduces  a  problem  on  which  there  is  some  differ- 
ence of  opinion  among  authorities.  However,  much  exper- 
imental evidence  is  available  and  in  many  sections  the 
results  of  proper  fertilization  can  be  predicted  with  consider- 
able certainty.  The  original  conceptions  of  this  problem 
were  based  largely  on  the  findings  of  the  chemists,  for  it 
seemed  logical  to  conclude  that  the  elements  found  in  the 
plant  and  its  products  in  greatest  amounts  were  the  ones  to 
return  to  the  soil  in  like  proportions.  This  doctrine  led  the 
horticulturists  somewhat  astray  for  a  time,  for  valuable  as 
it  is,  such  a  theory  does  not  take  into  consideration  the 
mechanical  or  physical  condition  of  the  soil  or  the  impor- 
tant role  of  micro-organisms  to  soil  fertility  and  the  asso- 
ciated factors  of  heat,  moisture,  and  soil  sanitation.  Obvi- 
ouslj^,  the  amount  of  artificial  "feeding"  that  trees  will 
require  depends  basicly  on  the  original  or  native  fertility 
of  the  soil  together  with  its  physical  condition  and  mois- 
ture-content. Hence  a  wide  variation  in  the  practical  re- 
sults of  fertilizing  orchards  is  to  be  anticipated,  especially 
in  the  relative  length  of  time  that  will  be  necessary  to  pro- 
duce like  results.  The  problem  should  be  studied  from  the 
standpoint  of  several  generations  of  trees  on  the  same  land, 
yet  the  longest  experiments  have  been  in  p-rogress  scarcely 
a  quarter  of  a  century. 

148.  Criticisms  of  orchard  experiments. — The  field 
tests  of  orchard  fertilizing  have  been  seriously  criticised 
179 


180  POMOLOGY 

from  several  points  of  view,  viz. :  (1)  The  soil  in  some  of  the 
experimental  orchards  has  been  exceedingly  variable  and  yet 
no  account  has  been  taken  of  that  fact  in  recording  the  ef- 
fects of  the  various  fertilizer  treatments.  (2)  Fruit-trees, 
particularly  large  apple  trees,  vary  exceedingly  in  the  size 
of  the  crop  they  produce,  and  averages  for  any  given  plot 
may  be  misleading.  (3)  When  buffer  rows  have  not  been 
maintained  between  the  plots,  there  has  not  infrequently 
been  cross  feeding  which  would  seriously  modify  the  re- 
sults. (4)  Missing  trees  in  an  orchard  may  give  certain 
advantages  to  those  adjacent  to  the  open  spaces,  and  also 
diseased  or  subnormal  individuals  may  not  give  a  repre- 
sentative result  of  the  treatments  used  in  an  orchard.  (5) 
Differences  of  topography  which  may  give  an  advantage 
to  certain  plots  over  others  because  of  unequal  frost  action 
and  drainage  have  often  played  a  large  part  in  results  se- 
cured, without  allowances  being  made  for  the  inequalities, 
often  without  mention  of  them.  (6)  Unwarranted  con- 
clusions have  been  drawn  of  the  value  of  a  single  element 
by  subtracting  the  performance  of  a  two-element  plot  from 
that  of  a  three-element  plot.  Many  other  suggestions  or 
criticisms  might  be  enumerated,  all  of  which  would  be  jus- 
tifiable in  critically  examining  this  problem. 

Without  question  it  is  more  difficult  to  select  uniform 
conditions  for  an  orchard  experiment  than  for  field  tests  of 
the  farm  crops,  and  the  available  data  are  open  to  criticism 
on  many  grounds.  Nevertheless,  this  field  work  has  been 
a  valuable,  if  not  a  necessary,  forerumier  of  the  more  tech- 
nical studies  of  a  physiological  nature  that  must  follow.  A 
number  of  valuable  economic  questions  have  already  been 
settled  and  much  of  the  previous  confusion  in  regard  to  or- 
chard fertilization  has  been  cleared  up. 

149.  Fertility  removed  by  fruit-trees. — Proceeding  from 
a  chemical  view-point,  the  amount  of  fertility  removed  by 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD    181 

fruit-trees  from  the  soil  will  give  a  basis  on  which  to  study 
the  plant-food  requirements  of  an  orchard.  Such  modifica- 
tions as  are  suggested  in  the  introductory  paragraph  will 
be  considered  later.  There  are  marked  variations  in  the 
analyses  reported  by  chemists,  due  probably  to  a  difference 
in  methods  and  to  the  varying  material  analyzed.  In  order 
to  obtain  a  satisfactoiy  set  of  figures,  Stewart  has  averaged 
a  large  number  of  analyses  of  the  apple  that  were  made 
in  both  America  and  Europe  and  reports  them  in  the  form 
of  percentage  of  diy  matter,  instead  of  on  the  basis  of  ash 
constituents  as  they  are  given  in  Chapter  I.  The  following 
table  summarizes  this  information: 


Table  LIII 
the  composition  of  apple  wood,  leaves,  and  fruit 


Plant 

Dry 

Nitrogen 

Phos. 
acid 

Potash 

Lime 

Magnesia 

Iron 

part 

stance 

(N) 

(P2O5) 

(K2O) 

(CaO) 

(MgO) 

(Fes-Oa) 

Pet. 

Pet. 

Pet. 

Pet. 

Pet. 

Pet. 

Pet. 

Wood  . 

52.25 

.62 

.20 

.36 

1,6 

.24 

.03 

Leaves 

34.45 

2.15 

.44 

1.34 

2.48 

.75 

.125 

Fruit.  . 

15.39 

.43 

.17 

1.10 

.08 

.09 

.02 

The  same  writer  has  made  a  comparison  of  the  total  draft 
of  an  apple  and  a  wheat  crop  to  the  acre,  assuming  vigor- 
ous and  productive  plants  in  each  case.  Such  a  collation 
is  of  interest,  for  it  has  usually  been  assumed  that  the  apple 
makes  a  lighter  draft  on  the  soil  in  comparison  with  a  grain 
crop.  Table  LIV  compares  the  plant-food  materials  util- 
ized by  the  two  crops. 


182 


POMOLOGY 


Table  LIV 

relative  amounts  of  plant-food  materials  removed  by  apples 
and  wheat 


IN   POUNDS   TO   THE   ACRE   ANNUALLY,    BASED   ON   THE 
INDICATED    IN   TABLE    LIII 

COMPOSITION 

Wood 

Leaves 

Fruit 

Apple 
(total) 

Wheat 
grain 

Wheat 
(total) 

Estimated  annual 
weights 

Lbs. 

3,500 
11.3 
3.6 
6.6 
29.1 
4.4 
0.5 

Lbs. 

3,500 

25.6 

5.3 

15.9 

29.5 

8.9 

1.5 

Lbs. 

24,500 
16.2 
6.4 
41.5 
3.0 
3.4 
0.8 

Lbs. 

31,500 
53.1 
15.3 
64.0 
61.6 
16.7 
2.8 

Lbs. 

1,500 
30.0 
10.0 
9.8 
0.84 
3.0 

Lbs. 

4,200 
43.7 
15.8 
26.8 

8.0 

6.1 

Nitrogen  (N) 

Phosphoric  acid  (PaOs) 

Potash  (K2O) 

Lime   (CaO) 

Magnesia  (MgO) 

Iron  (FeaOs) .  .  . 

Van  Slyke  has  summarized  his  data  for  the  several  tree- 
fruits  and  observes  that  the  quantity  of  nitrogen  and  pot- 
ash is  about  the  same  in  any  one  kind  of  tree,  while  the 
amount  of  phosphoric  acid  is  only  about  one-fourth  that  of 
the  other  two  materials.^ 


Nitrogen 30  to    75  pounds 

Phosphoric  acid 7    "    18       " 

Potash 33   "    72       " 

Calcium  oxide  (lime) 38    "114       " 

However,  the  amounts  used  by  different  kinds  of  fruit- 
trees  vary  greatly,  as  is  shown  by  the  table  on  opposite  page. 

According  to  studies  by  Thompson,^  "fruit-trees  demand 
plant  food  more  nearly  in  the  proportion  in  which  it  exists 
in  the  soil  than  does  com  or  almost  any  other  crop." 

^  Fertilizers  and  Crops.    New  York.    1912. 

2  Thompson,  R.  C.   Ark.  Agr.  Exp.  Sta.  Bull.  123  (Tech.).    1916. 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD    183 


Table  LV 
amount  of  mineral  plant-food  material  used  to  the  acre 

(after  VAN  SLYKE) 


Variety 


Apple. . 
Peach. . 
Pear.  .  . 
Plum.  . 
Quince . 


Number 
of  trees 

Nitrogen 

(N) 

to  the  acre 

lbs. 

35 

51.5 

120 

74.5 

120 

29.5 

120 

29.5 

240 

45.5 

Phosphoric 
acid 

(P^Os) 

lbs. 
14.0 
18.0 

7.0 

8.5 
15.5 


Potash 

Lime 

(K,0) 

(CaO) 

lbs. 

lbs. 

55.0 

57.0 

72.0 

114.0 

33.0 

38.0 

38.0 

41.0 

57.0 

65.5 

Magnesia 
(MgO) 

lbs. 
23 
35 
11 
13 
19 


150.  Fruit-trees  essentially  different  from  other  crops. — 

It  must  be  recognized  in  dealing  with  the  fertility  problem 
that  fruit-trees  are  essentially  different  from  other  crops 
because  of  their  greater  root  area  and  the  fact  that  a  large 
part  of  the  roots  may  be  found  in  the  subsoil.  This  means 
that  the  soil  will  support  a  fruit-tree  better  than  a  plant 
with  a  restricted  root  system.  Also  the  orchard  occupies 
the  land  for  many  years,  and  hence  the  problem  is  different 
from  that  in  which  a  rotation  of  crops  is  practiced.  The 
situation  is  also  more  complex  because  of  the  material  that 
is  returned  to  the  soil  from  the  leaves. 

151.  Amount  of  food  materials  found  in  plants  not  a 
guide. — The  relative  amounts  of  the  various  "essential" 
elements  in  the  tissues  of  the  plant  cannot  be  taken  as  an 
actual  guide,  because  the  soil  may  contain  an  abundance 
of  the  element  which  would  seem  to  be  most  necessary  to 
apply.  This  is  particularly  conspicuous  with  regard  to  pot- 
ash. According  to  the  data,  the  tree  uses  four  times  as  much 
potash  and  nitrogen  as  phosphoric  acid.  It  is  usual  to  find 
that  most  fruit  soils  are  relatively  rich  in  potash  which  ap- 
pears to  become  available  sufficiently  rapidly  by  good  tillage 


184  POMOLOGY 

methods.  Therefore,  instead  of  being  first,  potash  usually  is 
of  the  least  importance  of  the  three.  Similarly  nothing  in  the 
analysis  indicates  that  nitrogen  is  usually  of  first  importance, 
yet  this  is  commonly  preeminent.  Furthermore,  it  must  be 
recognized  that  more  food  may  be  taken  into  the  plant 
than  is  necessary  for  complete  functioning,  if  such  material 
is  present  in  the  soil  in  abundance  and  in  an  available  form. 
Jordan  ^  conducted  a  series  of  experiments  with  such 
crops  as  barley,  peas,  tomatoes,  tobacco,  buckwheat,  rape, 
and  turnips,  and  concludes  that  "the  results  secured  indi- 
cate that  what  a  grain  crop  contains  of  certain  elements  is 
not  necessarily  to  be  regarded  as  a  measure  of  what  must  be 
supplied  in  order  to  meet  the  needs  for  maximum  growth." 

152.  Analysis  of  the  soil  as  a  guide  to  fertilizing.— The 
question  naturally  arises  as  to  whether  a  chemical  analysis 
of  the  soil  would  be  a  guide  to  the  fertilizing  of  the  orchard, 
and  if  so,  what  element  in  particular  should  be  applied  and 
at  what  probable  rate.  While  it  would  seem  but  reasonable 
to  make  the  assumption  that  such  is  the  case,  yet  experience 
shows  that  the  plants'  requirements  can  be  only  roughly  ap- 
proximated in  this  way  and  that  errors  will  often  result  if 
dependence  is  placed  in  such  a  procedure. 

While  it  is  true  that  trees  on  poor  impoverished  land  will 
usually  be  notable  for  their  paucity  of  both  growth  and  yield, 
yet  if  the  physical  condition  of  the  soil  is  congenial,  a  good 
growth  may  be  secured  out  of  all  proportion  to  what  would 
be  expected  from  ordinary  farm  crops  on  the  same  soil.  This 
is  doubtless  accounted  for  at  least  in  part  by  the  greater 
feeding  area  of  the  root  systems  of  fruit-trees. 

153.  Necessity  of  fertilizing  orchards. — Whether  it  is 
necessary  to  fertihze  an  orchard  is  a  question  not  easily 
answered,  since  so  many  factors  are  involved.     The  prob- 

'  N.  Y.  Agr.  Exp.  Sta.  Bull.  360,  1913,  also  F.  R.  Pemper,  R.  I.  Agr. 
Exp.  Sta.  Bull.  169.    1917. 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD    185 

lem  should  be  viewed  without  prejudice  from  the  stand- 
point of  discovering  any  limiting  factor  to  maximum  results. 
If  insufficient  plant-food  is  available,  this  situation  should 
be  sensed  as  soon  as  possible  and  the  condition  relieved. 
It  will  depend,  however,  on  the  kind  of  trees,  the  soil,  the 
system  of  culture  followed,  the  age  of  the  trees,  and  finally 
on  the  results  of  these  conditions  as  manifested  in  the  trees 
themselves.  This  is  not  so  unsatisfactory  as  it  at  first  seems. 
An  experienced  grower  should  have  a  sufficiently  accurate 
knowledge  of  what  the  possibilities  of  trees  are,  to  determine 
whether  they  need  additional  fertility.  In  general,  the 
stone-fruits,  particular^  the  peach,  should  be  fertilized 
each  year  after  they  come  into  bearing.  The  apple  and  pear, 
when  grown  in  the  sod  or  mulch  system,  should  usually  be 
fertilized.  However,  exceptions  will  present  themselves;  and 
when  these  fruits  are  well  tilled  they  may  continue  for  many 
years  without  need  for  additional  plant-food  materials,  unless 
they  are  inter-cropped.  When  trees  are  nob  making  an  av- 
erage terminal  growth  of  at  least  several  inches  (6  to  12), 
when  the  foliage  is  not  a  rich  green  color  and  held  well  into 
the  fall,  and  when  they  are  not  bearing  good  crops  practi- 
cally every  year,  it  would  be  well  to  introduce  additional 
fertility  either  in  the  form  of  artificial  fertilizers  or  manures 
or  both.  However,  the  varietal  factor  enters  here  strongly; 
also  it  should  be  determined  whether  the  orchard  is  well 
drained  and  free  from  other  conditions  known  to  be  inju- 
rious. All  this,  of  course,  means  that  in  the  case  of  doubt  the 
only  definite  answer  can  be  obtained  by  the  local  test.  If 
a  response  is  secured  by  any  of  the  fertilizer  elements  or  a 
combination  of  them,  their  use  should  at  once  be  extended 
to  the  remainder  of  the  orchard.  Under  many  conditions, 
very  large  financial  returns  may  be  secured  from  the  use  of 
fertilizers;  it  is  not  wise  to  delay  applying  them  until  such 
marked  results  are  secured  as  on  some  of  the  impoverished 


186  POMOLOGY 

soils,  but  rather  to  maintain  continuously  a  vigorous  con- 
dition of  the  trees. 

154.  Fertilizing  tilled  and  non-tilled  apple  orchards. — 
The  source  of  much  error  in  studying  the  fertiUzer  problem 
in  the  apple  orchard  hes  in  a  failure  to  recognize  the  all  but 
universal  experience  in  fertilizing  a  tilled  and  a  sodded  plan- 
tation. The  fundamental  or  underlying  reasons  for  this 
difference  lie  in  the  effects  of  stirring  the  soil  on  its  nitrate 
and  moisture-content.  As  a  general  rule,  a  well-cultivated 
apple  orchard  (including  the  use  of  cover-crops)  will  respond 
slowly  to  the  use  of  chemical  fertilizers,  and  one  which  is 
not  tilled  will  give  prompt  returns.  An  outstanding  ex- 
ception is  in  the  impoverished  soils  of  southern  Ohio  where 
the  fertilizers  gave  as  great  and  as  prompt  results  in  tilled 
as  in  sod  orchards.  The  author  believes  this  is  of  such  im- 
portance that  the  fertilization  of  tilled  and  untilled  orchards 
are  considered  separately. 

155.  Moisture  and  fertility  intimately  related. — Moisture 
is  of  first  importance  in  the  proper  growth  and  develop- 
ment of  plant  and  fruit,  and  when  it  is  lacking  the  elements 
of  fertility  are  not  available.  If  the  soil  is  too  dry  at  a  crit- 
ical period,  the  fohage  suffers  and  the  fruit  is  small  and  of 
poor  quality.  On  the  other  hand,  too  much  water  in  the  soil 
is  equally  serious,  resulting  in  stunted  growth,  yellow  foli- 
age, and  eventually  death  of  the  trees.  Of  the  ten  or  more 
chemical  elements  that  enter  into  the  composition  of  the 
plant,  only  four  are  likely  to  require  special  attention  in  the 
way  of  amendments  to  the  soil.  These  are  nitrogen,  phos- 
phorus, potassium,  and  calcium.  Of  these  most  of  the  cal- 
cium (lime)  remains  in  the  wood  and  leaves,  while  a  large 
proportion  of  the  potassium  (potash)  finds  its  way  to  the 
leaves  and  fruit. 

156.  Relative  importance  of  the  different  essential 
elements. — While  each  of  these  so-called  essential  elements 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD    187 

is  necessary  for  tree  growth,  the  relative  necessity  of  their 
appUcation  to  the  soil  will  depend  on  the  amount  already 
available  and  the  quantity  taken  up  by  any  given  kind  of 
plant.  There  has  been  much  misunderstanding  and  erroneous 
teaching  regarding  this  question  in  pomology.  However, 
the  field  experiments  have  done  much  to  clear  up  the  situa- 
tion, although  there  is  still  a  lack  of  conclusive  information. 

157.  Organic  versus  inorganic  fertilizers. — In  compar- 
ative tests  on  the  use  of  organic  fertilizers,  such  as  dried 
blood,  tankage,  and  cotton-seed  meal,  and  such  inorganic 
materials  as  nitrate  of  soda,  acid  phosphate,  basic  slag,  and 
nmriate  or  sulfate  of  potash,  the  conclusion  is  reached  that 
the  inorganic  materials  are  usually  to  be  preferred. 

In  an  Ohio  experiment  ^  two  orchards  badly  in  need  of 
nitrogen  show  the  following  results  as  a  five-year  average 
in  pounds  of  fruit  to  a  tree: 


Table  LVI 

comparative  valxje  op  inorganic  and  organic  forms  of  fertilizer 

(after  ballou) 


Application  to  a  tree 

1st  orchard 

2d  orchard 

5  pounds  nitrate  of  soda 
5  pounds  acid  phosphate 
2H  pounds  muriate  of  potash 

Lbs. 
205.8 

Lbs. 
317.6 

5  pounds  tankage 

5  pounds  bone-meal 

23/2  pounds  muriate  of  potash 

Lbs. 
93.8 

Lbs. 
1G3.9 

158.  Value  of  nitrogen. — One  of  the  most  outstanding 
results    of    the    various   fertilizer    experiments    conducted 
throughout  the  country  is  the  importance  of  applying  ni- 
1  Ohio  Agr.  Exp.  Sta.  BuU.  30L    1916. 


188  POMOLOGY 

trogen  in  a  soluble  form  when  an  orchard  is  low  in  vitality. 
Such  a  treatment  is  of  much  more  importance  to  an  or- 
chard which  is  not  tilled  since  it  has  been  shown  that  the  soil 
nitrates  are  likely  to  be  greatly  reduced  under  those  cir- 
cmnstances.  This,  of  course,  will  depend  on  the  conditions 
of  the  soil  and  perhaps  on  the  climate,  for  some  notable  cases 
are  on  record  in  which  an  application  of  nitrogen  to  a  culti- 
vated orchard  gave  immediate  and  striking  results.  If  an 
orchard  experiment  is  continued  for  a  very  long  period,  the 
time  is  likely  to  come  when  nitrogen  may  be  applied  with 
profit  whatever  the  cultural  system  followed. 

In  point  of  efficiency  in  maintaining  the  growth  and  yield 
of  the  trees,  nitrogen  stands  alone  among  the  artificial  fer- 
tilizers. 

159.  Nitrate  of  soda. — This  carrier  of  nitrogen  is  more 
commonly  used  than  any  other  because  of  its  solubility. 
The  results  are  usually  prompt  and  marked.  When  this 
fertilizer  is  used  alone,  it  often  gives  as  good  results  for  the 
first  few  years  as  when  in  combination  with  carriers  of  phos- 
phoric acid  and  potash.  However,  over  a  series  of  years, 
a  complete  fertihzer  is  considered  best.  The  amount  nec- 
essary varies  with  the  age  of  the  trees,  their  condition,  and 
the  type  of  soil  involved.  Nitrate  of  soda  is  also  used  as  a 
special  "stimulant"  for  trees  that  are  sub-normal  as  a  result 
of  injury,  having  been  employed  with  success  on  winter- 
injured  trees,  those  hurt  by  fire  or  other  agencies. 

For  mature  apple  trees,  the  usual  application  is  from  4 
to  6  pounds  to  a  tree  or  approximately  150  to  200  pounds 
to  an  acre.  Smaller  trees  receive  proportionately  less  unless 
the  application  is  made  over  the  entire  orchard  surface. 
For  the  peach,  an  application  of  2}^  to  ^Yz  pounds  to  a 
tree  is  usually  sufficient. 

160.  Sulfate  of  ammonia  is  also  a  readily  available  form 
of  nitrogen  and  from  a  knowledge  of  its  effects  on  other 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD    189 

crops,  it  would  seem  to  be  adapted  to  orchard  use.  Unfor- 
tunately, sufficient  data  are  not  as  yet  available  to  warrant 
a  definite  statement  of  its  value,  but  in  demonstration  tests 
the  results  have  fully  equaled  those  of  nitrate  of  soda.  Rei- 
mer  ^  used  sulfate  of  ammonia  in  an  experiment  with  Winter 
Nelis  pears  in  the  Rogue  River  Valley,  Oregon,  and  finds 
that  "The  plot  which  received  5  pounds  of  sulfate  of  am- 
monia produced  a  notable  increase  in  yield,  almost  equaling 
the  yield  produced  by  10  pounds  of  nitrate  of  soda.  The 
5  pounds  of  sulfate  of  anmionia  contains  as  much  nitro- 
gen as  63^2  pounds  of  nitrate  of  soda."  Other  experimental 
work  in  Oregon  with  both  the  peach  and  apple  demonstrate 
that  this  material  is  of  increasing  importance  in  orchard 
work.  With  certain  of  the  field  crops,  however,  it  has  been 
found  that  this  source  of  nitrogen  is  not  quite  equal  to  the 
same  units  of  nitrogen  in  nitrate  of  soda.  Also  the  chemi- 
cal changes  which  take  place  will  ultimately  exhaust  the 
bases  of  the  soil  unless  the  land  is  well  supplied  with  cal- 
cium or  else  lime  is  applied  to  offset  the  loss. 

161.  Time  of  application. — So  far  as  is  now  known,  the 
quickly  available  forms  of  fertilizers  should  be  applied  not 
later  than  blossom  time  to  secure  the  best  results,  and  it 
is  convenient  to  add  all  materials  at  the  same  time  whether 
they  are  readily  soluble  in  water  or  not.  They  may  be 
broadcast  on  top  of  the  grass  or  mulch  or  sown  with  a  fer- 
tilizer drill  in  the  case  of  a  tilled  orchard. 

There  seems  to  be  some  definite  evidence  to  show  that  an 
application  of  nitrate  of  soda  about  two  weeks  before  the 
blossoms  open  will  greatly  stimulate  the  "set"  of  fruits  of 
the  apple,  this  being  particularly  noticeable  on  weak  trees. 
This  seems  to  have  been  reported  first  by  Ballon  -  from  work 
in  southern  Ohio.     An  orchard   of   twenty-year-old  Rome 

» Ore.  Agr.  Exp.  Sta.  Bull.  166.     1920. 
-  Ohio  Agr.  Exp.  Sta.  Bull.  301.     1916. 


190  POMOLOGY 

apples  which  had  produced  but  one  crop  of  fruit  because 
of  its  extremely  low  vitality,  was  fertilized  in  part  about 
the  middle  of  April.  ''The  trees  bloomed  rather  uniformly 
over  the  entire  orchard,  but  the  blossoms  were  unusually 
small  and  apparently  lacking  in  vitality.  However,  after 
the  petals  of  the  blossoms  had  fallen,  the  little  apples  on  the 
fertilized  plots  where  nitrate  of  soda  had  been  included 
clung  to  the  fruit  spurs  and  began  to  grow  in  a  perfectly 
normal  manner,  while  most  of  the  embryo  fruits  on  the  ad- 
joining unfertilized  plots  withered  and  dropped  from  the 
tree  just  as  the  apples  had  been  doing  throughout  the  past 
life  of  the  orchard."  At  picking  time  of  this  first  year  one 
row  of  eight  trees  which  was  fertiUzed  with  a  5-5  nitrate- 
phosphate  combination  produced  twenty-one  barrels  of  fruit, 
while  the  adjoining  untreated  row  yielded  nine  barrels. 

The  same  effect  of  an  early  application  of  nitrate  on  the 
set  of  blossoms  is  reported  by  Lewis.  He  finds  that  as  a 
result  they  secured  a  higher  percentage  of  ''set,"  an  imme- 
diate change  in  character  of  foliage,  and  a  stimulation  of 
wood  growth. 

162.  Phosphorus  is  rather  low  in  many  soils  and  in 
animal  manures,  but  is  required  in  less  amounts  by  fruit- 
trees  than  either  nitrogen  or  potassium  (in  the  relation  of 
4N,  1  P2O5,  4K2O)  as  was  seen  above.  However,  the  data 
in  regard  to  this  element  are  rather  unsatisfactory  and  in- 
consistent in  the  orchard  experiments.  It  would  seem  to 
rank  next  to  nitrogen  in  its  requirement  as  an  amendment 
to  the  soil,  although  when  applied  alone  the  results  are 
frequently  meager  or  negative.  An  exception  is  found  in 
certain  sections  where  phosphoric  acid  has  had  a  positive 
result  in  encouraging  the  growth  of  clov^er  in  a  sod  orchard 
(see  Ohio  experiments)  which  in  turn  is  beneficial  to  the  soil. 

163.  Acid  phosphate. — As  a  carrier  of  phosphoric  acid, 
this  material  seems  to  give  the  most  satisfactory  results 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD    191 

because  of  its  availability.    It  is  commonly  used  at  the  rate 
of  350  to  400  pounds  to  the  acre. 

Both  floats  and  basic  slag  have  been  used  in  orchard  ex- 
periments with  vaiying  results,  but  neither  has  been  so  effi- 
cient as  acid  phosphate.  Bone-meal  has  not  proved  valu- 
able in  securing  results  within  a  reasonable  length  of  time 
and  it  is  not  so  widely  used  in  orchards  as  formerly. 

164.  Potash  is  used  by  fruit-trees  in  relatively  large 
amounts.  This  led  to  the  earlier  teachings  that  potash 
was  the  first  essential  in  fertilizing  fruit-trees.  This  theoiy 
ignored  the  fact  that  many  fruit  soils  are  comparatively  rich 
in  potash  and  hence  obviated  the  necessity  of  adding  it  in 
an  artificial  form.  The  statements  that  potash  fertilizers 
make  better  color,  better  shipping  quality  and  flavor  of 
fruits  are  without  apparent  foundation  in  experimental 
results.  When  potash  is  applied  alone  or  in  combination, 
the  data  show  few  instances  in  which  outstanding  results 
are  secured  from  it. 

165.  Muriate  versus  sulfate  of  potash. — Some  differ- 
ence of  opinion  exists  as  to  the  relative  value  of  muriate 
and  sulfate  of  potash  for  orchard  use.  Both  have  given 
satisfactoiy  results  where  there  was  need  for  a  potash  fer- 
tilizer. Therefore,  since  the  muriate  is  cheaper,  it  would 
seem  good  practice  to  apply  it  until  further  research  shows 
a  superiority  of  the  sulfate. 

166.  Hardwood-ashes. — Wood-ashes  have  long  been  used 
for  fruit-trees  and  were  highly  valued  a  half  century  ago, 
but  their  scarcity  at  the  present  time  has  greatly  re- 
stricted their  use.  Wood-ashes  will  vaiy  markedly  in  their 
composition;  if  they  are  unleached  they  will  analyze  about 
4  to  6  per  cent  potash,  1.5  to  2  phosphoric  acid,  and  25  to 
30  per  cent  lime.  Potash  salts  have  largely  replaced  wood- 
ashes  as  a  source  of  potassium  in  orchard  fertilization. 

167.  Common   salt. — Sodium   chloride   has   been   advo- 


192  POMOLOGY 

cated  for  orchards  (at  the  rate  of  about  150  pounds  to  the 
acre)  to  release  the  potash  in  the  soil  and  thus  furnish 
the  trees  with  that  element.  Since  potash  is  not  often  the 
limiting  factor,  this  practice  is  not  of  importance  to  the 
orchardist.  Some  such  reaction  as  the  following  is  believed 
to  take  place  in  the  soil: 

NaCl  -h  KAlSiaOs  =  NaAlSisOg  +  KCl. 

168.  Animal  manures  in  the  orchard. — In  several  of  the 
fertilizer  experiments  already  cited,  the  value  of  manure  for 
the  orchard  has  been  shown.  When  it  is  used  on  a  sodded 
or  mulched  orchard,  it  not  only  furnishes  plant-food  but, 
what  is  often  quite  as  valuable,  it  conserves  the  moisture. 
As  a  top  dressing  in  a  sod  orchard  it  is  slower  acting,  how- 
ever, and  on  the  whole  less  effective  than  nitrate  of  soda, 
when  nitrogen  is  badly  needed.  In  a  tilled  orchard  it  is 
valuable  as  a  source  of  organic  matter  as  well  as  of  plant- 
food. 

That  the  experimental  results  from  its  use  are  variable  is 
shown  by  results  in  two  orchards  which  seemed  similar.^ 
In  one  was  obtained  an  aiuiual  cash  gain  to  the  acre  for  five 
years  of  $20.75,  while  in  another  the  gain  was  $110.75,  or 
$2.00  an  acre  less  than  the  adjoining  plot  treated  with  ni- 
trate of  soda  alone.  Unfortunately,  these  data  are  not  given 
in  terms  of  yield. 

From  work  conducted  in  Pennsylvania  ^  •  it  is  reported 
that  ''in  ten  similar  experiments,  the  gains  from  stable  ma- 
nure in  both  tilled  and  unfilled  treatments  have  averaged 
79.3  bushels  per  acre  annually,  while  those  from  commer- 
cial fertilizer  averaged  73.0  bushels.  In  five  cases  involving 
tillage,  however,  the  gains  from  the  fertilizer  have  averaged 
99.6  bushels  per  acre  annually,  while  those  from  the  manure 

1  Ohio  Agr.  Exp.  Sta.  Bull.  301.    1916. 

2  Penn.  Agr.  Exp.  Sta.  Bull.  141.    1916. 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD    193 

have  averaged  only  83.4  bushels.  In  general,  therefore, 
the  manure  has  surpassed  the  fertilizer  on  untilled  trees  and 
has  been  surpassed  by  it  on  those  receiving  tillage.  The 
extra  mulching  effect  of  the  manures  has  doubtless  contrib- 
uted to  this  result." 

EXPERIMENTS  IN  UNTILLED  ORCHARDS 

As  stated  in  the  foregoing  paragraphs,  the  most  marked 
results  from  fertilizing  have  been  secured  in  orchards  that 
are  not  cultivated,  and  some  typical  cases  may  be  cited  to 
show  the  results  attained. 

169.  The  Massachusetts  experiment.^ — In  Massachu- 
setts a  fertilizer  test  was  conducted  in  an  orchard  of  Graven- 
stein,  Baldwin,  Roxbuiy  Russet,  and  Rhode  Island  Green- 
ing apples  for  a  period  of  fifteen  years.  Three  trees  of  each 
of  these  varieties  were  included  to  a  plot.  They  were  planted 
in  1890  and  cultivated  for  five  years.  From  1895  until 
1910,  the  trees  were  in  sod,  and  the  following  list  of  treat- 
ments together  with  the  total  yield  of  fruit  for  this  period 
summarizes  the  results: 


Table  LVII 

RESULTS  OF  ORCHARD  FERTILIZATION MASSACHUSETTS.    (aFTER  BROOKS) 


Plot 

Fertilizer 

Annual  rate 
to  the  acre 
— pounds 

Total 
yield  for  15 
years — pounds 

1 

20,000 
2,000 

600 
200 
600 
400 

24,934 

2 

Wood-ashes 

12,841 

3 

Nothing                              

3,940 

4 

Bone-meal             

14,453 

5 

Bone-meal 

Low-grade  sulfate  of  potash 

21,863 

Mass.  Agr.  Exp.  Sta.,  22d  Ann.  Rept.,  Part  2.    1910. 


194  POMOLOGY 

This  experiment  shows  the  superiority  of  any  of  the  treat- 
ments over  the  untreated  plot.  The  striking  point,  in  the 
Hght  of  later  investigations,  is  the  absence  of  an  application 
of  quickly  available  nitrogen  for  this  orchard.  The  manure 
has  given  outstanding  results  in  yield  and  growth,  no  doubt 
due  to  the  supply  of  nitrogen  it  carried  as  well  as  to  the 
organic  matter  added  to  the  soil.  Brooks  states  that  too 
much  manure  was  used,  for  the  trees  made  too  heavy  a 
growth  and  the  fruit  was  green  and  coarse.  This  is  a  com- 
mon experience  when  trees  are  over-fertilized  with  animal 
manures.  Perhaps  the  most  outstanding  result  of  this  ex- 
periment is  the  apparent  superiority  of  the  low-grade  sul- 
fate of  potash,  which  contains  a  large  amount  of  magnesia, 
over  the  bone-meal-muriate-of-potash  treatment.  The  dif- 
ferences in  the  two  plots  may  have  been  due  to  the  pres- 
ence of  magnesium  as  the  sulfate  or  chlorid  or  to  the  sul- 
fur itself  in  the  sulfates  of  potassium  and  magnesium,  but 
the  cause  or  causes  for  the  difference  in  behavior  have  not 
been  clearly  established.  The  effect  of  wood-ashes,  which 
contain  about  1  to  2  per  cent  of  phosphoric  acid  (P2O5)  and 
4  to  6  per  cent  of  potash  (K2O),  is  of  interest  since  the  com- 
mon recommendation  of  the  older  horticulturists  was  to  use 
wood-ashes  for  fruit-trees. 

170.  The  Ohio  experiments. — Further  light  is  thrown  on 
this  problem  by  the  Ohio  experiments  in  which  a  mulch  is 
usually  included.  This  work  was  conducted  in  the  southern 
part  of  the  state  on  land  low  in  native  fertility,  and  where 
the  surface  soil  is  very  thin,  usually  supporting  a  cover  of 
poverty-grass  {Danthonia  spicata)  and  weeds.  The  land 
washes  or  erodes  badly  and  hence  it  is  not  deemed  wise  to 
cultivate  it. 

This  experiment  gave  immediate  results  when  nitrogen 
was  used  alone  or  in  combination  with  fertilizers  carrying 
phosphoric  acid  or  potash.    The  beneficial  effects  continued 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD    195 

each  year,  and  clenionstrated  beyond  question  that  the  first 
and  most  important  need  for  these  orchards  was  a  qaickly 
available  form  of  nitrogen.  Nitrate  of  soda  proved  to  be 
the  bftst  carrier  of  nitrogen.  When  phosphoric  acid  was 
used  in  combination  with  nitrate  of  soda  or  in  a  complete 
fertilizer,  there  was  little  or  no  evidence  that  it  was  a  Umit- 
ing  factor,  although  the  soil  is  naturally  low  in  phosphorus. 
However,  it  proved  of  great  value  in  securing  a  stand  of 
better  grasses  as  is  discussed  in  connection  with  producing 
mulch  material.  Neither  did  potash  have  any  apparent 
effect  in  increasing  the  vigor  or  yield  of  the  trees  during 
the  five-year  test.  These  conclusions  are  supported  by  the 
following  summaiy  of  the  data: 

Table  LVIII 

average  yield  to  a  tree  in  3  orchards  of  rome  beauty  apples, 
22-25  years  old.l    grass-mulch 

5-year  average.     (after  ballou) 


Treatment  ^ 


1st 

2d 

Orchard 

Orchard 

Lbs. 

Lbs. 

69.9 

124.1 

315.6 

296.3 

205.8 

317.6 

93.8 

163.9 

214.2 

96.0 

133.7 

100.1 

124.1 

3d 
Orchard 


Checks 

Nitrate 

N  it  rate — phosphorus — potash . 

Duphcate 

Tankage — bone — potash 

Nitrate — phosphorus 

Potash 

Manure 


Lbs. 
122.6 
378.9 
348.4 
315.9 


1  Loc.  oil. 

2  The  followino;  amounts  of  fertilizer  were  u-sed  in  each  case: 


Nitrate  of  soda,  5  lbs. 
Acid  phosphate,  5  lbs. 
Muriate  of  potash  2^/^  lbs. 


Stable  manure  250  lbs. 
Tankage  5  lbs. 
Bone  5  lbs. 


196  POMOLOGY 

In  a  later  report,^  an  additional  experiment  is  recorded 
which  confirms  the  earlier  findings  on  the  type  of  soil  in 
southern  Ohio.    Other  features  of  interest  are  also  included. 

In  1914,  a  twenty-year-old  orchard  of  Rome  Beauty  and 
Ben  Davis  apples  which  were  very  low  in  vitality  and  en- 
tirely non-productive  was  secured  for  the  purpose  of  exper- 
imentation. Two  rows  of  twelve  trees  each  constituted  a 
plot,  the  one  having  the  fertilizer  distributed  in  a  circle 
beneath  the  tree,  and  the  other  having  it  applied  over  the 
entire  tree  square  ("all-over  method").  A  check  or  buffer 
row  was  maintained  between  each  two  plots.  Half  the  or- 
chard was  cultivated  and  a  cover-crop  sown  amiually,  and 
the  other  half  was  put  under  the  grass-mulch  system,  the 
fertilizer  treatments  being  the  same  on  both  sections.  There 
was  no  material  difference  in  yield  between  the  "circle" 
and  the  "all-over,"  method  of  distributing  the  fertilizer,, 
but  the  latter  encouraged  a  strong  growth  of  vegetation 
for  mulching  purposes. 

The  conclusions  of  this  experiment  are  striking  in  several 
particulars,  notably  in  showing  that  fertilizer  will  produce 
equally  prompt  and  valuable  results  in  both  tilled  and 
mulched  orchards  in  that  section,  an  end  not  secured,  under 
a  number  of  other  conditions,  as  discussed  later  in  this  chap- 
ter. Also  tillage  alone  will  not  suffice  to  produce  maximum 
crops  on  the  soil  in  question. 

If  the  unfertilized  grass-mulch  plot  is  taken  as  the  check, 
the  following  increases  obtain  for  a  five-year  average: 

1  Ohio  Agr.  Exp.  Sta.  Bull.  339.    1920. 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD    197 

Table  LIX 

results  from  fertilizing  tilled  and  mulched  orchards — 
southern  ohio.    (adapted  from  ballou  and  lewis) 


Percentage 

Average  yield 
to  the  acre, 

increase 

5-yr.  period 

Barrels 

Grass  mulch— unfertilized 

0 

37.6 

Cultivation — cover-crops  unfertilized 

41 

53.2 

Grass  mulch — fertilized 

100 

75.4 

Cultivation— cover-crops  fertilized 

95 

73.5 

The  more  complete  data  are  given  in  the  following  table: 


Table  LX 
effect  of  fertilization  on  tilled  and  grass-mulch  orchard — ohio. 

(after   BALLOU  AND  LEWIS) 


Row 
No. 


Cultivated  plot 


Nitrate  of  soda,  5  lbs.  on  tree  circle 

Nitrate  of  soda,  5  lbs.  on  tree  square 

No  fertilizer 

Nitrate  of  soda,  5  lbs. ;  acid  phosphate,  5  lbs.  on  tree 
circle 

Nitrate  of  soda,  5  lbs. ;  acid  phosphate,  5  lbs.  on  tree 
square 

No  fertilizer 

Nitrate  of  soda,  5  lbs. ;  acid  phosphate,  5  lbs. ;  muri- 
ate of  potash,  5  lbs.  on  tree  circle 

Nitrate  of  soda,  5  lbs. ;  acid  phosphate,  5  lbs. ;  muri- 
ate of  potash,  5  lbs.  on  tree  square 

Totals  for  cultivated  plot 


5-year 

average, 

1914-18 


Lbs. 
3,220.1 
3,017.2 
2,270.8 

3,081.6 

2,950.6 
2,308.0 

2,935.7 

3,407.5 


23,191.3 


198 


POMOLOGY 


Table  LX — Continued. 


Row 
No. 


Grass-mulch  plot 


Nitrate  of  soda,  5  lbs.  on  tree  circle 

Nitrate  of  soda,  5  lbs.  on  tree  square 

No  fertilizer 

Nitrate  of  soda,  5  lbs. ;  acid  phosphate,  5  lbs.  on  tree 
circle 

Nitrate  of  soda,  5  lbs. ;  acid  phosphate,  5  lbs.  on  tree 
square 

No  fertilizer 

Nitrate  of  soda,  5  lbs.;  acid  phosphate,  5  lbs.;  muri- 
ate of  potash,  5  lbs.  on  tree  circle 

Nitrate  of  soda,  5  lbs. ;  acid  phosphate,  5  lbs. ;  muri- 
ate of  potash,  5  lbs.  on  tree  square 


Totals  for  grass-mulch  plot 22,970 . 3 


5-year 
average 
1914-18 


Lbs. 
2,817.9 
2,295.5 
1,503.7 

3,799.7 

3,641.3 
1,773.5 

3,287.6 

3,851.1 


171.  The  Pennsylvania  experiments  ^  confirm  the  above 
results  in  general,  with  some  modifications.  Again  nitro- 
gen has  proved  the  most  important  element  in  increas- 
ing the  growth  and  yield  of  apple  trees  in  sod,  although  the 
other  elements  have  seemed  to  be  of  greater  importance 
here  than  in  the  Ohio  work.  In  a  summary  statement  Stew- 
art says,  "The  addition  of  phosphorus  or  potassium  to  ni- 
trogen applications  has  usually  given  larger  returns  than 
nitrogen  alone.  The  nitrogen  and  phosphorus  combina- 
tion has  produced  an  average  increase  over  the  normal  yields 
in  two  experiments  of  265  and  308  bushels  per  acre  amiually 
during  9-  and  10-year  periods.  This  combination  is  also 
proving  important  in  one  of  the  experiments  in  young  or- 
chards.    In  at  least  three  of  the  other  bearing  orchards. 


Loc.  cit. 


Plate  \'. — a,  Kiiut  ivom  :in  unthiiiiuHl  liukhviii  aiii)l('  iroo;  7  Inishels 
No.  1  fruit  imd  17  ])ushels  No.  2  fruit,  b,  Fruit  from  a  thinned 
Baldwin  tree;  19  bushels  No.  1  fruit  and  1)^  bushels  No.  2  fruit. 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD    199 

however,  the  addition  of  phosphorus  has  resulted  in  no  im- 
portant benefit."  Also,  "Potash  has  increased  the  yields 
materially  in  three  of  the  experiments  in  bearing  orchards 
and  apparently  has  shown  some  value  in  increasing  the  size 
of  the  fruit.  It  has  also  apparently  had  an  injurious  effect 
in  two  of  the  eight  experiments.  It  would  seem  advisable 
therefore,  to  defer  its  general  use  in  any  particular  orchard 
until  definite  evidence  of  its  value. is  secured."  Manure 
has  usually  had  a  beneficial  effect,  although  it  is  slower 
acting  than  nitrate  of  soda.  These  conclusions  are  supported 
by  the  following  data: 


Table  LXI 

10-year  summary   of   results  in  fertilizing    apple  orchards  in 

pennsylvania.    yield  to  the  acre  in  bushels  (after  stewart) 


Treatment 
Trees  in  sod  or  grass  mulch 

Baldwin, 
mature 
orchard 

York,  Baldwin, 
mature 
orchard 

Bu. 

228 
488.6 
450.9 
291.8 

479.9 

519. 

Bu. 
Ill 

Nitrogen  and  phosphoric  acid 

Nitrogen  and  potash  as  muriate 

Phosphorus  and  potash  as  muriate 

Phosphorus  and  potash  as  sulfate 

Nitrogen,  phosphorus,  and  potash 

Nitrogen 

486.1 

318.2 

113.1 

91.3 

292.2 
186  2 

405.1 

The  kind  and  amounts  of  fertilizer  commonly  used  in  the 
Pennsylvania  experiments  are  shown  in  table  on  page  200. 


200 


POMOLOGY 


Table  LXII 


AMOUNT  OF  FERTILIZER  TO  THE  ACRE  FOR  BEARING  TREES 
(after    STEWART) 


Nitrogen 

Phosphoric  acid 

Potash 

SO  lbs.     (N) 

50  lbs.     (P2O5) 

25  to  50  lbs.     (K2O) 

Carried  in: 

Carried  in: 

Carried  in: 

100  lbs.  nitrate  of  soda 

350  lbs.  acid  phosphate 

50  to  100  lbs.  muriate 

and 

or  in 

of  potash 

150  lbs.  dried  blood 

200  lbs.  bone-meal 

or  in 

or  in 

or  in 

100  to  200  lbs.  of  low- 

150  lbs.  ammonium  sulfate 

300  lbs.  basic  slag 

grafle  sulfate 

172.  New  Hampshire  experiments. — In  order  to  de- 
termine to  what  extent  the  results  from  grass-mulch  or- 
chards could  be  duplicated  under  the  conditions  existing 


Fig.  29. — Row  of  trees  to  l(^ft  were  fertilized  with  5  pounds  nitrate 
of  soda  each.    Those  to  right  were  untreated. 

in  New  Hampshire,  a  test  was  arranged  in  a  mature  Bald- 
win orchard  which  was  producing  low  yields.  It  had  not 
been  cultivated  for  several  years,  the  grass  being  cut  for  hay 
and  removed  annually.  The  results  secured  by  the  treat- 
ments were  quite  similar  to  those  obtained  from  the  exper- 
iments just  reviewed  and  demonstrate  that  the  grass-mulch 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD    201 

system  of  orcharding  has  wide  apphcation.     Table  LXIII 
gives  the  treatments  and  the  results  secured  for  three  years. 

Table  LXIII 

YIELD  OF  BALDWIN  APPLES  IN  A  RENOVATED  ORCHARD  (nEW  HAMPSHIRE) 

ALL   TREES   MULCHED   WITH   200   POUNDS   SWAMP   HAY   TO    A   TREE 

YIELD    A   ROW    (8   TREES)    IN   BARRELS 


Row 
\o. 

Treatment 

1916 
Barrels 

1917 
Barrels  i 

1918 
Barrels 

Average 
3  years 

Barrels 
to  the  acre 

1 

7  lbs.  basic  slag  to  a  tree .  . 

13.50 

4.50 

31.3 

16.43 

71.75 

2 

5  lbs.  nitrate  of  soda 

20.63 

5.33 

27.8 

17,92 

77.35 

3 

3  lbs.  sulfate  of  potash 

13.92 

3.29 

19.2 

12.13 

52.85 

4 

Check 

9.48 

3.30 

24.1 
35 .  36 

12.29 

53.55 

5 

28.88 

6.97 

23.73 

103  60 

5  lbs.  nitrate  soda 

6 

5  lbs.  acid  phosphate 

3  lbs.  sulfate  potash 

8.91 

4.50 

35.60 

16.33 

71.40 

7 

7.52 

2.90 

19.04 

9.82 

43.05 

3  lbs.  sulfate  potash 

8 

Check 

12.42 

2.89 

10.32 

10.54 

45.85 

9 

5  lbs.  nitrate  soda 

3  lbs.  sulfate  pota.sh    

21.08 

4.51 

20.24 

15.27 

66.85 

10 

5  lbs.  acid  phosphate 

4.76 

2.46 

16.0 

7.74 

33.95 

Ave.  check  rows,  4  and   8 

10.95 

3.09 

20.21 

11.41 

49.70 

Ave.   nitrogen  rows,  2,  5,  9 

23.53 

5.60 

27.80 

18.97 

82.73 

Ave.  potash  and  phosphoric 
acid  rows,  1,  3,  6,  7,  10... 

9.72 

3.53 

24.23 

12.49 

54.60 

EXPERIMENTS  IN  TILLED  ORCHARDS 

It  has  been  stated  that  a  cultivated  apple  orchard  usually 
responds  much  more  slowly  to  the  use  of  fertilizers  than  a 
sodded  or  mulched  one,  although  there  are  conditions  in 
which  the  response  is  as  himiediate  as  in  the  latter  case. 
While  the  former  cases  predominate,  some  standard  experi- 
ments will  be  cited  in  which  the  trees  have  not  responded  to 
fertilization  and  others  in  which  results  were  obtained. 
1  Computed  in  part  from  total  yield,  approximately  correct. 


202  POMOLOGY 

173.  The  Wobum  experiment.^— At  the  Woburn  Ex- 
perimental Fruit  Farm  (England),  a  cultivated  orchard  was 
treated  annually  for  fourteen  years  and  at  the  completion 
of  the  work  the  following  conclusion  was  drawn:  "Neither 
moderate  nor  heavy  dressings  of  dung  or  artificial  fertilizers, 
nor  of  both  combined,  had  any  appreciable  effect  on  any 
feature  of  the  trees  nor  on  the  crops  from  them.  The  total 
effect  did  not  amount  to  5  per  cent  and  even  that  effect  was 
doubtful.  The  only  exception  was  in  the  case  of  nitrate  ap- 
plied in  the  early  summer  which  in  several  seasons  produced 
a  good  effect." 

Later  Pickering  reports  the  following:^  "The  results  ob- 
tained at  Ridgmont  during  twenty-two  years  lead  to  the 
conclusion  that  the  apple  trees  which  have  been  dressed 
every  year  throughout  that  period  with  various  dressings 
of  artificial  or  natural  manure  have  shown  no  appreciable 
advantage  over  similar  trees  which  received  no  dressing 
whatever.  Whilst  this,  however,  has  been  the  case  with 
dwarf  and  standard  apple  trees,  and  also  mixed  with  plan- 
tations of  apples,  pears,  and  plums,  the  reverse  has  proved 
to  be  the  case  with  bush  fruits,  such  as  currants,  goose- 
berries, and  raspberries:  those  which  were  left  umnanured 
have  been  practically  exterminated,  whilst  those  which  were 
manured  flourished.  But  the  manure  which  was  essential 
in  these  cases  was  a  bulky  organic  manure,  such  as  dung, 
since  artificial  manures  p'roduced  but  little  more  effect 
than  no  manure  at  all." 

174.  The  New  York  experiments. — Hedrick  reports 
on  a  twelve-year  experiment  ^  in  a  mature  orchard  in  New 
York,  showing  that  neither  lime,  potash,  nor  phosphoric  acid 
had  any  practical  effect  on  the  growth  or  yield  of  the  trees. 

1  Woburn  Expt.  Fruit,  Farm.    4th  and  5th  Rept.    1904-05. 

2  Science  and  Fruit  Growing.    London.     1919.    pp.  89-90. 

3  N.  Y.  Agr.  Exp.  Sta.  Bull.  289.    1907. 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD    203 

The  varieties  involved  were  Baldwin,  Fall  Pippin,  Rhode 
Island  Greening,  Roxbury  Russet,  and  Northern  Spy. 
Clean  culture  was  followed  annually  until  August  1,  when  a 
cover-crop  of  oats,  barley,  or  clover  was  sown.  Wood-ashes 
were  applied  at  the  rate  of  100  pounds  to  a  tree  and  also  in 
the  last  seven  years  83^  pounds  of  acid  phosphate  to  a  tree. 
The  conclusion  drawn  is  that:  "The  returns  obtained  in 
this  twelve-year  experiment  are  negative  from  a  practical 
standpoint.  The  experiment  shows  that  it  is  not  profitable 
to  apply  potash,  phosphoric  acid,  or  lime  to  the  soil  of  this 
orchard.  Fifty-seven  years  of  orchard  cropping  has  not 
reduced  this  soil  to  the  condition  where  it  needs  a  'complete' 
fertilizer,  yet  the  leguminous  cover  crops  plowed  under  in 
the  orchard  have  usually  produced  beneficial  effects  the 
same  or  the  next  season.  .  .  .  An  interesting  fact  is 
that  both  treated  and  untreated  plots  increased  mark- 
edly in  yield  from  1893  to  1904.  The  probable  explanation 
is  that  prior  to  1893  the  orchard  was  in  sod  but  during  the 
experiment  it  was  kept  under  cultivation  and  grew  more 
productive  under  the  treatment." 

In  another  experiment  ^  conducted  in  a  younger  orchard, 
a  similar  lack  of  response  from  the  use  of  fertilizers  is  reported 
after  fifteen  years'  work.  The  variety  was  Rome  Beauty 
top-worked  on  Ben  Davis.  The  following  results  were  se- 
cured from  the  treatments: 

I  N.  Y.  Agr.  Exp.  Sta.  Bull.  339.    1911. 


204 


POMOLOGY 


Table  LXIV 

YIELD  AND  GROWTH  FROM  FERTILIZER  TREATMENTS   (AFTER  HEDRICK) 


Treatment 

Average  yield 

to  a  tree, 
7-yr.  average 

Average 

diameter  of 

trunk  at  end  of 

experiment  (1910) 

Stable  manure 

Acid  phosphate 

Muriate  of  potash 

Acid  phosphate 

Muriate  of  potash 

415.15 
12.66 
7.26 
12.6 

7.26 
12.60 

3.67 
12.84 
92.25 

Lbs. 
90.47 

87.57 

103.34 

99.10 
92.25 

In. 
6.26 
5.98 

6.35 

Nitrate  of  soda 

6.18 

Check 

6.14 

It  will  be  seen  from  these  data  that  the  fertilizers  have 
resulted  in  practically  no  increases  in  growth  or  yield  of 
the  trees.  Neither  was  there  a  difference  in  the  uniformity 
of  the  crops  or  in  the  maturity,  keeping  quality,  texture,  or 
flavor  of  the  fruit.  It  is  recorded  that  the  size  of  the  apples 
was  slightly  increased  by  the  treatments  and  that  the  foli- 
age was  greener  during  the  last  season  of  the  experiment 
where  nitrogen  had  been  applied.  But  the  conclusion  was 
drawn  that  "The  trees  in  this  experiment  would  have  been 
practically  as  well  off  had  not  an  ounce  of  fertilizer  been  ap- 
plied to  them." 

After  twenty  years'  work  in  this  same  orchard,  the  con- 
clusions are  drawn  that,  "In  general  there  are  so  many  in- 
conclusive or  contradictory  results  that  no  conclusion  of 
practical  value  can  be  drawn  from  the  yields.  Heavy  appli- 
cations of  nitrogen  in  a  complete  fertilizer  and  in  manure 
have  not  increased  tree  growth.     When  the  costs  are  con- 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD   205 

sidered,  certain  plats  have  given  increases  sufficient  to  equal 
the  costs,  or  even  to  show  a  profit,  but  in  other  plats  the 
same  plant  food  elements  have  shown  a  financial  loss."  ^ 

175.  The  New  Hampshire  experiments.— A  somewhat 
similar  experiment  -  was  conducted  by  the  New  Hampshire 
Station.  The  orchard,  which  consisted  of  about  300  mature 
Baldwin  trees,  was  situated  on  a  light  soil.  It  was  found, 
after  ten  years,  that  the  use  of  a  complete  fertilizer  had  de- 
cidedly increased  the  growth  of  the  trees  and  that  after 
the  sixth  year  a  better  general  appearance  and  darker  green 
color  was  evident.  This  is  in  contrast  with  the  New  York 
experiment  involving  a  heavier  and  richer  soil,  where  such 
a  difference  was  nol  evident  until  the  fifteenth  year.  How- 
ever, after  twelve  years'  treatment,  the  fertilized  plots 
failed  to  respond  in  yield  of  frint,  as  they  had  made  very- 
slight  gains  and  in  some  cases  none  over  the  first  stimulus 
of  the  cultivation.  An  increase  in  size  of  the  fruit,  however, 
was  distinctly  noticeable,  especially  in  the  plot  receiving 
the  following  treatment  high  in  potash:  2  pounds  nitrate  of 
soda,  10  pounds  sulfate  of  potash,  and  8}^  pounds  acid  phos- 
phate to  a  tree  (Plot  10).  It  was  observed,  however,  that 
an  increase  in  yield  of  fruit  was  to  be  expected  in  the  near 
future  because  of  the  greater  size  of  trees,  and  hence  bearing 
surface.  This  is  in  accord  with  much  of  the  work  con- 
ducted in  well-tilled  orchards,  some  requiring,  however,  much 
longer  to  show  the  need  of  artificial  "feeding"  than  others. 
In  fact,  some  may  never  reach  the  point  at  which  it  would 
be  economical  to  apply  fertiUzers.  The  following  table 
shows  not  only  the  effect  of  the  fertilizers  but  also  other  cul- 
tural treatments  as  discussed  in  the  previous  chapter: 

1  Hedrick,  U.  P.,  and  R.  D.  Anthony.  Twenty  years  of  fertilizers  in 
an  apple  orchard.    N.  Y.  (Geneva)  Agr.  Exp.  Sta.  Bull.  460.    1919. 

2  Gourley,  J.  H.  Sod,  tillage  and  fertilizers  for  the  apple  orchard. 
A  ten-year  summary.    N.  H.  Agr.  Exp.  Sta.  Bull.  190.    1919. 


206  POMOLOGY 

Table  LXV 
average  annual  yield  to  the  acre  in  bushels  (1909-1918) 
Plot 
1        Sod 99 

4  Clean  tillage 191 

5  Tillage  cover-crops 196 

6  To  the  acre: 
70  lbs.  nitrate 

245  lbs.  basic  slag 188 

140  lbs.  sul.  potash 

7  To  the  acre: 
70  lbs.  nitrate 

298  lbs.  acid  phos 154 

140  lbs.  sul.  potash 

8  To  the  acre:  ' 
70  lbs.  nitrate 

695  lbs.  acid  phos 145 

140  lbs.  sul.  potash 

9  To  the  acre: 
210  lbs.  nitrate 

298  lbs.  acid  phos 160 

140  lbs.  sul.  potash 
10  To  the  acre: 

70  lbs.  nitrate 

298  lbs.  acid  phos 176 

350  lbs.  sul.  potash 

176.  The  Maine  experiment. — Much  the  same  result 
has  been  obtained  in  the  Maine  experiments.  A  mature 
Ben  Davis  orchard  of  400  trees  was  divided  into  three  plots 
and  the  following  treatments  given:  Plot  A  has  had  no 
fertilizer  since  1912;  plot  B  has  received  amiually  since  1912, 
500  pounds  to  the  acre  of  a  fertilizer  carrying  4  per  cent  ni- 
trogen, 8  per  cent  available  phosphoric  acid,  and  7  per  cent 
potash;  plot  C  has  been  given  annually  since  1912,  1000 
pounds  to  the  acre  of  a  4-8-7  fertilizer.  For  three  years 
prior  to  1912  the  entire  orchard  was  cultivated  and  fertilized 
at  the  rate  of  1000  pounds  to  the  acre  of  a  4-8-7  fertilizer 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD  207 

which  of  course  comphcates  the  matter  but  the  results  after 
eight  years  may  be  summarized  as  follows:  "Exact  records 
of  yields  and  measurements  of  growth  have  been  taken  since 
the  experiment  was  begun.  No  differences  that  could  be 
attributed  to  the  additional  nitrogen  (or  other  ingredients) 
in  the  fertilizer  have  been  noticed."  ^ 

177.  The  Oregon  experiments. — An  interesting  example 
of  the  influence  of  commercial  fertilizers  on  a  cultivated 
orchard  of  bearing  apple  trees  is  shown  by  the  work  of 
Lewis  and  Brown  in  Oregon.-  The  soils  were  exhausted 
by  continual  clean  cultivation  without  the  use  of  green- 
crops  to  maintain  the  supply  of  organic  matter.  Neither  was 
irrigation  practiced  in  order  to  supply  the  necessary  moisture. 
As  a  result,  the  soils  "lacked  water-holding  capacity,  they 
baked  or  puddled  early,  and  on  hillsides  were  given  to  ero- 
sion." Two  years'  work  demonstrated  that  no  response  of 
a  practical  nature  could  be  expected  from  the  use  of  potash 
or  phosphoric  acid,  but  when  nitrogen  was  supplied  the  ef- 
fect was  immediate.  This  would  seem  to  be  a  special  case 
in  which  the  soil  had  reached  the  point  of  exhaustion  of 
available  nitrogen,  and  hence  would  no  longer  support  the 
trees  satisfactorily.  Even  though  all  these  soils  were  cul- 
tivated frequently  and  part  of  them  continually,  the  appli- 
cation of  nitrogenous  fertilizer  gave  as  quick  returns  as 
when  it  is  added  to  a  run-down  sodded  orchard.  The  appar- 
ent exception  here  to  the  general  premise  in  this  text  is  prob- 
ably largely  explained  by  the  authors  of  the  work  as  follows: 
"We  are  all  familiar  with  the  fact  that  shade  crops  induce 
bacterial  action  and  by  liberating  nitrogen,  stimulate  tree 
growth.  There  are  many  evidences  to  show  that  alfalfa, 
left  pennanently  in  the  orchard,  does  not  stimulate  wood 
growth  as  rapidly  as  where  placed  in  a  shorter  rotation  with 

1  Me.  Agr.  Exp.  Sta.  Bull.  236,  260. 

2  Rept.  1916.    Hood  River  Branch  Exp.  Sta.,  p.  37. 


208  POMOLOGY 

clean  tillage.  The  same  rule  to  some  extent  applies  to  clover. 
In  the  former  case,  miless  receiving  an  abmidance  of  water, 
often  not  the  case,  and  care  such  as  renovation  and  cultiva- 
tion in  its  somewhat  unnatural  environment,  this  shade 
crop  does  not  make  its  best  growth,  and  becomes  soddy,  a 
condition  not  only  inimical  to  its  own  welfare,  but  to  that  of 
the  trees  as  well.  On  the  other  hand,  when  organic  matter 
such  as  clover  or  alfalfa  is  turned  under  frequently,  say  once 
in  every  three  or  four  years,  and  followed  by  clean  tillage, 
disintegration  of  organic  matter  and  bacterial  action  are 
greatly  accelerated,  inducing  great  vigor  of  tree,  especially 
in  '  off '  years  when  the  crop  is  light."  It  is,  therefore,  recog- 
nized that  on  the  soils  in  question  the  nitrate  was  applied 
as  a  special  measure  and  gave  excellent  results,  but  that  such 
a  treatment  would  probably  not  have  been  necessary  had 
a  better  system  of  soil  management  been  followed.  It  should 
also  be  stated  in  this  connection  that  alfalfa  may  remain 
in  the  orchard  for  a  period  of  years  when  properly  handled 
without  injury  to  the  trees. 

The  data  in  Tal)le  LXVI  give  a  summary  of  this  work. 

178.  West  Virginia  experiment.^ — The  experiments  con- 
ducted in  the  Ohio  Valley  on  impoverished  soils,  which 
were  under  cultivation,  corroborates  the  results  secured  in 
southern  Ohio.  Nitrogen  proved  to  be  of  first  importance 
in  obtaining  a  vigorous  growth  of  trees  and  maximum  yield 
of  fruit.  When  phosphorus  was  used  in  connection  with 
nitrogen,  the  results  were  somewhat  greater  than  was  se- 
cured from  the  latter  alone,  but  the  chief  value  of  the  phos- 
phorus seems  to  have  been  in  promoting  a  greater  growth 
of  cover-crops  and  sod  coverings.  Potash  apparently  gave 
no  response  in  these  orchards. 

lAlderman,  W.  H.,  and  H.  L.  Crane.  W.  Va.  Agr.  Exp.  Sta.  Bull.  174. 
1920. 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD   209 


Table  LXVI 
results  on  spitzenburg  apple  trees  from  use  of  nitrate  of  soda 

(after  LEWIS   AND  BROWN) 


Orchard  > 

Plot 

I'uuiids  to  n  tree. 
Nitrate  of  xoda 

Treatment, 

3-yr.  ave. 

to  a  tree 

1914-1916. 

Ave.  ter- 
minal growth. 

1914 

1915 

Yield  loose 
boxes 

1914-1916 

1 

1.  a 

5.2 

5.2 

Clover 

8.4 

20.1 

2.  b 

5.2 

5.2 

Green-manure 

7.8 

17.1 

3.  c 

5.2 

5.2 

"            " 

5.3 

16.1 

4. 

No  ferti 

izer 

Check 

3   1 

19.9 

2 

1.  a 

6.75          C.75 

Alfalfa  sod 

8.8 

15.4 

2.  b 

6.75          6.7.5 

9.2 

8.4 

3.  c 

6.75          6.75 

11.8 

14.7 

4. 

No  fertilizer 

Cheek 

2.9 

5.2 

Lbs.  nitrate 

to  a  tree 

3 

1. 

7.3 

16.1 

11.7 

No  treatment 

5.0 

13.44 

9.9 

3. 

None 

8.56 

4.1 

4. 

3.0 

12.61 

14.1 

4 

1. 

7.3 

6.08 

17.4 

2 

5.0 

4.72 

20.1 

3. 

None 

1.77 

4.7 

4. 

3.0 

5.78 

17.7 

In  cultivated  orchards  in  the  eastern  part  of  West  Virginia 
where  the  soil  is  more  fertile,  the  response  from  fertiliza- 
tion was  practically  negligible  after  eight  years'  work. 

179.  The  Pennsylvania  experiments.— The  Pennsyl- 
vania Station  -  reports  a  set  of  experiments  in  tilled  or- 
chards which  is  not  in  harmony  with  several  of  the  others 
considered.  It  was  found  that  under  the  conditions  of  their 
experiments,  both  manure  and  artificial  fertilizers  have 
given  as  good  results  in  a  cultivated  as  in  a  sod  orchard. 
"In  six  cases  with  tillage,  the  gains  from  commercial  ferti- 

1  Orchards  Nos.  1  and  2. 

a.  Fertilizer  broadcast  on  ground. 

b.  Fertilizer  sprayed  on  ground  as  liquid. 

c.  Fertilizer  sprayed  on  ground  and  tree  as  liquid. 
Orchards  Nos.  3  and  4. 

Treatment  began  in  1916.    All  broadcast  on  ground. 

2  Penn.  Agr.  Exp.  Sta.  Bull.  153. 


210 


POMOLOGY 


lizer  have  averaged  90.3  bushels  per  acre,  and  only  69.1  bush- 
els in  the  six  corresponding  cases  without.  Tillage,  there- 
fore, has  increased  the  efficiency  of  the  fertilization  in  most 
cases.  There  were  several  important  exceptions,  however, 
and  tillage  excesses,  either  in  depth  or  frequency,  may  actu- 
ally reduce  the  gains  from  fertilization."  These  conclu- 
sions are  supported  with  the  following  data: 

Table  LXVII 
ten-year  summary  of  results  in  fertilizing  tilled  apple  orchards 

(after  STEWART) 


Treatment 


York, 

Stayman, 

Young  orchard 


Ave.  of  checks 

Nitrogen  and  phosphorus 

Nitrogen  and  potash 

Phosphorus  and  muriate 

Phosphorus  and  sulfate 

Nitrogen,  phosphorus,  and  potash. 

Nitrogen 

Manure 


225.7 
279.1 
350.4 
292.4 
293.4 
298.5 
236.8 
304.2 


180.  The  Ohio  experiments. — A  discussion  of  these 
experiments  was  included  under  the  section  on  "untilled 
orchards,"  since  a  comparative  statement  in  that  place 
seemed  more  desirable. 

181.  Results  compared. — It  is  confusing  to  find  such 
contradictory  statements  from  a  similar  type  of  experiment, 
but  the  student  should  understand  that  it  is  the  duty  of  the 
experimenter  to  report  faithfully  the  results  of  his  work 
without  prejudice  in  regard  to  the  results.  When  it  becomes 
evident  that  the  worker  is  endeavoring  to  prove  instead  of 
to  find  out  something,  the  interpretation  of  his  work  is 
weakened  proportionately. 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD   211 

It  is  possible  that  the  difference  in  results  is  due  largely 
to  the  organic  matter  in  the  soil.  In  a  climate  where  the 
season  is  long  and  the  suramer  heat  intense,  cultivation 
would  "bum  out"  the  organic  matter  or  source  of  nitrogen 
much  more  quickly  than  where  the  opposite  conditions 
obtain.  Also  a  soil  already  devoid  of  organic  material 
would  probably  produce  the  same  results.  It  is  at  least 
worthy  of  notice  that  three  of  the  experiments  here  consid- 
ered in  which  fertilizers  in  a  cultivated  apple  orchard  were 
very  slow  in  producing  results  were  in  the  North  (Maine, 
New  Hampshire,  and  New  York). 

OTHER  RESULTS  OF  FERTILIZING 

182.  Color  of  fruit. — In  general,  it  may  be  stated  that  no 
fertilizer  combination  yet  tried  will  increase  the  color  of 
fruit  appreciably.  In  some  apple  experiments  there  seemed 
to  be  a  slight  advantage  to  color  from  potash  but  not  suffi- 
cient to  warrant  its  use  for  this  purpose.  Alderman  ^  gave 
double  and  triple  applications  of  potash  to  plots  of  peaches 
and  reports  that  there  is  "absolutely  no  effect  upon  color 
of  fruit,  a  fact  which  indicates  the  worthlessness  of  this 
material  as  a  coloring  agent."  In  the  case  of  a  number  of 
crops,  phosphoric  acid  will  hasten  maturity,  but  this  has 
not  been  observed  with  the  apple. 

It  has  not  infrequently  been  stated  that  iron  salts  will 
heighten  the  red  color  of  fruits,  and  several  well-planned 
experiments  have  been  prosecuted  to  determine  this  point. 
At  the  Woburn  Experimental  Fruit  Farm  ^  where  such  a 
test  was  made,  it  was  concluded  after  twenty-two  years' 
work  that  where  2.8  grains  of  iron  sulfate  to  a  square  meter 
or  a  similar  amount  of  manganese  sulfate  was  used,  no  ef- 
fect had  been  noticed  on  fruit  color  with  the  exception  of 

1  W.  Va.  Asr.  Exp.  Sta.  Bull.  150.     1915. 

2  Woburn  Exp.  Fruit  Farm.     16th  Rept.    1917. 


212  POMOLOGY 

one  year,  and  this  was  attributed  to  chance.  Conversely, 
tillage  or  the  use  of  nitrogen  fertilizers  or  manure  commoaly 
cause  a  profusion  of  foliage  which  shades  the  fruit  and  re- 
duces coloring;  it  also  delays  maturity  and  hence  may  lessen 
the  red  color  of  fruit. 

In  other  words,  the  development  of  color  in  fruit  is  largely 
dependent  on  maturity  and  the  free  action  of  sunlight.  If 
fruits  are  bagged  while  green,  they  will  not  develop  red  color 
unless  the  bag  itself  is  translucent  to  the  extent  of  letting 
some  light  pass  through  when  some  proportionate  color  will 
develop.^  Where  fogs  occur  and  the  intensity  of  the  light 
is  decreased,  the  color  of  the  fruit  is  lower,  and  the  converse 
holds  true. 

183.  Fertilizing  the  peach. — It  is  not  necessary  to 
consider  separately  the  fertilization  of  tilled  and  untilled 
peach  orchards,  since  rarely  is  this  fruit  grown  without  cul- 
tivation. The  outstanding  fact  to  be  considered  here  is  that, 
unlike  the  cultivated  apple  orchard,  the  peach  will  usually 
respond  readily  to  proper  fertilization,  particularly  after 
the  trees  reach  bearing  age. 

Chemical  data  show  that  the  peach  is  a  heavy  feeder  and 
removes  large  quantities  of  plant-food  from  the  soil.  It  is 
particularly  striking  that  this  fruit  removes  nitrogen  and 
potash  in  great  excess  over  phosphorus.  This  fact  is  well 
illustrated  in  Table  LXVIII  adapted  from  Alderman:  ^ 

Since  it  has  been  shown  that  the  peach  uses  large  quan- 
tities of  the  soil  ingredients  in  comparison  with  most  other 
fruits,  it  might  be  anticipated  that  it  should  require  rather 
heavy  fertilization  for  best  results.  That  the  growth  of  the 
trees  and  yield  of  fruit  are  affected  by  proper  fertilizing  is 
shown  by  the  following  condensed  table  of  the  results  se- 
cured by  the  West  Virginia  Experiment  Station: 

1  Blake,  M.  A.    Rept.  Soc.  Hort.  Sci.     1913. 

2  W.  Va.  Agr.  Exp.  Sta.  Bull.  150.    1915. 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD   213 

Table  LXVIII 
plant-food  removed  to  the  acre  a  year  by  the  peach 


Nitrogen 

Phosphoric 
acid 

Potash 

New  Jersey  (173  trees) 

64  lbs. 
75    " 
69.5" 

IS  lbs. 
18    " 
18    " 

40  lbs. 

New  York  (120  trees)    

72    " 

Average 

56    " 

Nitrate  of 
soda 
463 

167o  acid 

phosphate 

112.5 

Muriate 

of  potash 

112 

Table  LXIX 

EFFECT  OF  FERTILIZERS  ON  PEACH  TREES  (ADAPTED  FROM  ALDERMAN) 


Treatment  ' 


^ 

^"7 

1, 

'SS^ 

^^ 

e   e 

-^5 

1?  ^ 

^ 

^ 

Lbs.  to 

the  tree 

Percent 

Sq.  in. 

69.95 

80.6 

4.28 

71.93 

75.5 

4.26 

72.06 

74.0 

4.06 

49.48 

58.0 

2.63 

42.42 

57.9 

2.89 

82.29 

76.0 

4.12 

82.09 

75.2 

4.39 

82.59 

76.2 

4.26 

60.82 

64.4 

3.26 

^  i 


Nitrogen  and  phosphoric  acid . 

Nitrogen  and  potassium 

Complete 

C  'heck 

Potash  and  acid  phosphate. .  . 

Complete 

Complete  with  double  potash. 
Complete  with  potash  tripled. 
Lime 


Inches 
16.1 
14.47 
15.0 

8.16 
7.28 
14.40 
15.59 
15.0 
7.84 


■  N  =  200  lbs.  nitrate  of  soda  to  the  acre. 

P205  =  335  lbs.  acid  phosphate  (16%)  to  the  acre. 

K  =  135  lbs.  muriate  of  potash  to  the  acre. 


214  POMOLOGY 

The  above  experiment  with  bearing  peach  trees  was  con- 
ducted for  four  years.  The  soil  in  question  was  a  shale  loam 
and  "low  in  fertihty,"  and  each  plot  contained  twenty  trees 
of  Carman  and  Waddell  varieties.  As  a  result  of  the  treat- 
ments with  nitrate  of  soda,  the  annual  growth  of  the  trees 
was  double  that  of  the  untreated  ones.  The  yield  was  nearly 
doubled  also  by  the  use  of  nitrogen  but  it  delayed  maturity 
by  several  days,  which  in  some  cases  was  advantageous  from 
a  commercial  standpoint.  Neither  the  element  phosphorus 
nor  potassium  produced  any  beneficial  effects  and  some  in- 
jurious consequences  followed  the  use  of  the  latter. 

The  influence  of  lime  could  not  be  definitely  determined 
and  was  regarded  as  largely  negative,  although  the  produc- 
tion was  somewhat  increased. 

The  trees  which  did  not  receive  nitrogen  produced  fruit 
of  higher  color,  but  the  cause  was  attributed  to  the  extra 
sunshine  which  reached  the  fruit,  owing  to  the  sparse  and 
sickly  foilage. 

It  is  commonly  stated  that  a  limestone  soil  is  markedly 
better  than  a  non-calcareous  one,  but  this  statement  is 
open  to  question,  depending  on  what  shall  be  considered 
such  a  soil  and  what  is  to  be  grown.  Fruit-trees  use  lime  in 
considerable  quantities  and  would  not  thrive  if  the  supply 
of  carbonate  of  lime  in  the  soil  was  veiy  low,  any  more  than 
other  plants.  However,  as  indicated  before,  it  is  not  neces- 
sary to  have  a  so-called  limestone  soil  for  the  production  of 
any  of  the  common  fruits.  It  is  claimed  that  the  "stone" 
fruits  require  more  lime  than  the  pome-fruit,  although  data 
are  lacking  to  establish  this  statement.  Lewis  ^  reports 
that  his  work  with  lime  on  stone-fruits  has  given  no  benefits 
to  the  trees.  On  the  other  hand,  lime  seems  to  have  been  of 
some  benefit  to  peach  trees  in  the  "Eastern  Pan-handle"  of 
West  Virginia  but  no  effect  was  noticed  on  the  fruit  itself. 
1  Ore.  Agr.  Exp.  Sta.  Bull.  166.    1920. 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD   215 

It  is  of  course  well  established  that  lime  will  increase  ni- 
trification in  the  soil,  but  orchard  experiments,  and  many  are 
on  record,  do  not  show  much  benefit  from  its  use.  The  inter- 
crops and  cover-crops,  on  the  other  hand,  may  require  it 
and  as  soon  as  this  can  be  determined,  lime  should  ])e  applied. 

184.  Effect  of  fertilizing  on  regular  bearing. — It  is 
usually  found  that,  unless  weather  or  other  external  causes 
interfere,  fruit-trees  that  respond  to  tillage,  fertilizer,  or 
both  will  be  more  regular  in  their  bearing  than  those  that 
are  somewhat  below  normal.  It  has  been  observed  that  well- 
fertilized  trees  are  noticeably  more  productive  in  a  season 
unfavorable  for  setting  fruit  or  following  a  severe  winter 
than  untreated  individuals.^ 

185.  Application  of  fertilizers.— When  fertilizers  are 
ai)])lied  to  a  mulched  or  sodded  orchard,  they  are  merely 
broadcasted  on  the  mulch  or  over  the  entire  orchard  area 
as  the  case  may  be,  and  the  succeeding  rains  dissolve  and 
carry  them  into  the  soil.  This  is  usually  done  about  the 
time  the  blossoms  are  ready  to  open,  although  in  the  case  of 
nitrate  of  soda  it  may  be  applied  earlier.  When  fertilizers 
arc  added  to  a  tilled  orchard,  they  are  usually  applied  after 
it  is  .plowed  and  perhaps  harrowed  once  in  the  spring,  thus 
incorporating  them  with  the  soil  early  in  the  growing  season. 

186.  Size  of  fruit  is  influenced  largely  by  the  amount 
which  a  tree  has  set.  Good  cultural  methods  will  increase 
the  size  provided  they  do  not  result  in  an  overload  of  the 
trees,  in  which  case  the  size  may  not  be  maintained.  Ferti- 
lizers, especially  those  containing  a  liberal  amount  of  potash, 
seem  to  have  some  effect  in  increasing  size.  Whenever 
moisture  is  well  maintained,  the  size  is  increased.  Manure 
will  often  produce  excessively  large  and  coarse  fmits. 

Yomig  trees  are  likelj^  to  produce  over-sized  fruit,  even  to 
the  point  of  losing  some  of   the  normal  characteristics  of 
1  N.  J.  Agr.  E.\p.  Sta.  Ann.  Kept.  1884-94. 


216  POMOLOGY 

the  variety.     Thinning  has  a  greater  effect  on  increasing 
size  on  a  heavily  ladened  tree  than  any  other  practice. 

187.  Summary.^ — The  following  statements  summarize 
the  general  conclusions  which  may  be  drawn  from  the  fore^ 
going  discussion: 

1.  The  most  fundamental  difficulty  in  interpreting  the 
experiments  in  orchard  fertilization  is  due  to  failure  to 
recognize  whether  or  not  an  orchard  is  tilled. 

2.  Apple  orchards  in  sod  or  grass  mulch  usually  require 
fertilization  to  maintain  the  growth  and  yield  of  the  trees. 

3.  Orchards  which  are  being  well  cultivated,  involving 
the  use  of  some  cover-crop,  are  likely  to  respond  rather 
slowly  to  the  use  of  chemical  fertilizers,  and  when  such  bene- 
fit appears  it  is  usually  first  seen  in  growth  rather  than 
in  yield. 

4.  The  length  of  time  which  an  orchard  under  cultiva- 
tion can  be  operated  without  supplying  additional  fertility 
will  depend  on  the  initial  fertility  of  the  soil. 

5.  Nitrogen  is  likely  to  be  the  first  limiting  factor  so  far 
as  soil  fertility  is  concerned.  This  one  element  is  likely  to 
give  as  good  results  for  a  few  years  as  a  complete  fertilizer, 
although  on  some  soils  the  latter  would  be  more  desirable 
in  the  end. 

6.  This  element  (nitrogen)  then  may  be  supplied  in  either 
of  two  ways,  by  the  use  of  the  plow  and  harrow  or  from  the 
fertilizer  bag. 

7.  A  peach  orchard  (which  should  always  be  cultivated) 
will  respond  generously  to  the  use  of  fertilizers  unless  it  is 
for  the  first  two  or  three  years  after  planting. 

8.  Red  color  of  fruit  is  apparently  not  affected  except 
adversely  by  fertilizing. 

9.  Size  of  fruit  is  variously  affected  by  fertilizing.      A 

1  Author's  statement.  Proc.  N.  Y.  State  Hort.  Soc,  2nd  Ann.  Meet- 
ing.   1920.    pp.  92-93. 


FERTILIZERS  AND  MANURES  FOR  THE  ORCHARD   217 

veiy  heavy  crop,  due  to  the  treatment,  may  result  in  a  de- 
crease in  the  size  of  the  individual  fruits,  or  if  a  moderate 
crop  is  produced  the  fruits  may  be  markedly  increased  in 
size.  Potash  appears  to  be  of  some  importance  in  increasing 
size. 

10.  An  orchard  which  is  inter-cropped  should  usually 
be  manured  or  fertilized. 

11.  So  far  as  apple  trees  are  concerned,  the  addition  of 
lime  is  rarely  necessaiy,  but  it  may  be  veiy  desirable  for  the 
cover-  or  inter-crop  grown.  Peach  trees  have  occasionally 
responded  to  applications  of  hme. 

12.  Inorganic  forms  of  artificial  fertilizers  seem  to  give 
prompter  results  than  the  organic  ones. 

13.  Yield  and  growth  go  "hand  in  hand"  and  are  not 
antagonistic. 

14.  An  early  application  of  nitrogen  (in  a  quickly  avail- 
able form)  will  often  stimulate  the  "set"  of  fruit  the  same 
season  and  hence  give  immediate  results. 


CHAPTER  X 
THE  RELATION  OF  CLIMATE  TO  POMOLOGY 

The  relation  of  climate  to  horticulture  and  agriculture  is 
very  intimate  and  is  almost  the  ultimate  determinant  of 
what  shall  be  grown.  The  orchardist  feels  that  he  has 
reached  the  frontier  of  his  knowledge  and  ingenuity  in  at- 
tempting to  combat  the  elements  and  overcome  their  devas- 
tating effects.  Other  factors,  of  course,  determine  where 
and  what  crops  can  be  grown,  but  climate  becomes  the  ac- 
tual determinant  as  the  northern  and  southern  limits  for 
special  crops  are  reached. 

While  the  forester  studies  the  climatic  conditions  best 
adapted  to  certain  types  of  tree  growth  and  then  does  his 
planting  accordingly,  the  horticulturist  must  consider  the 
climatic  peculiarities  and  causes  of  failure  and  then  deter- 
mine means  of  overcoming  them.  It  is  also  true  that  insect 
and  disease  pests  are  more  abundant  and  more  destructive 
some  seasons  than  others,  owing  to  favorable  weather  con- 
ditions, and  the  grower  must  accordingly  modify  his  plans 
to  combat  them  successfully. 

188.  Terms  defined. — Climate  has  been  defined  as  the 
average  condition  of  the  atmosphere,  while  weather  denotes 
a  single  occurrence,  or  event,  in  the  series  of  conditions  that 
make  up  climate.  The  climate  of  a  place  is,  then,  in  a  sense 
its  average  weather.  Phenology  is  the  science  of  the  rela- 
tions between  chmate  and  periodic  biological  phenomena, 
such  as  the  flowering,  leafing,  and  fruiting  of  plants. 

The  particular  natural  phenomena  constituting  climate 
that  are  of   special    interest    in   this   connection  are,  tem- 
perature, rainfall,  wind,  sunlight,  frost,  hail,  and  humidity. 
218 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    219 

189.  Relation  of  weather  to  the  fruit  crops. — The  weather 
may  specifically  affect  the  fruit  crop  for  any  given  season 
in  two  general  ways:  (1)  it  may  govern  largely  the  poten- 
tial possibilities  of  the  trees  to  form  fruit-buds;  and  (2)  it 
may  partially  or  entirely  destroy  the  buds,  blossoms,  or 
crop  in  the  process  of  development.  These  effects  of  weather 
on  the  fruit-crop  may  be  subdivided  as  follows:  (a)  the 
nature  of  the  growing  season  may  be  favorable  or  unfavor- 
able to  a  set  of  fruit-buds  for  the  ensuing  se<ason;  (b)  the 
winter  may  be  favorable  to  or  may  destroy  the  fruit-buds 
previously  formed;  (c)  the  spring  weather  may  be  responsi- 
ble for  the  partial  or  entire  loss  of  the  fruit  crop  due  to  frosts 
at  blooming  time  or  shortly  thereafter;  (d)  special  agencies 
such  as  hail  or  wind  may  partially  or  entirely  destroy  the 
maturing  crop;  (e)  rainy  weather  or  heavy  winds  may  prevent 
pollination  of  the  blossoms  in  whole  or  in  part;  (f)  low  tem- 
peratures may  check  pollen-tube  growth;  (g)  the  quality  of  a 
crop  and  the  size  of  the  individual  fruits,  as  well  as  their  early 
or  late  maturity,  is  often  governed  largely  by  the  weather. 

190.  Temperature  is  the  most  important  climatic  element 
affecting  veg(>tation  and  the  total  effect  of  the  warmth  of 
the  air  nuist  be  observed  in  studjdng  it.  There  is  a  minimum 
and  maxumim  temperature,  below  or  above  which  the  plant 
does  not  function,  and  there  is  for  each  kind  an  optimum  tem- 
perature at  which  it  grows  or  functions  best.  The  minimum 
for  most  higher  plants  is  around  40°  to  43°  F.  and  the  maxi- 
mum is  from  85°  to  114°  F.,  while  the  optima  range  from 
75°  to  85°  F.,  depending  in  all  cases  on  the  species  in  ques- 
tion. Since  the  various  phases  of  the  plants '  functions  may 
have  different  optima  and  since  it  is  also  difficult  to  define 
closely  these  terms,  the  above  temperatures  should  be  con- 
sidered as  applying  particularly  to  the  more  manifest  growth 
activities.  The  student  of  pomology  is  interested  in  both 
the  temperatures  of  the  growing  season  and  those  of  winter, 


220  POMOLOGY 

for  much  damage  may  occur  from  too  low  or  too  high  tem- 
peratures during  the  winter  rest.  The  latter  are  treated  in 
Chapter  XL 

Many  fruit  sections  are  accmnulating  data  on  which  fu- 
ture plantings  may  be  based  with  greater  intelligence.  The 
mean  amiual  temperature  or  the  mean  of  the  365  successive 
daily  means  is  a  figure  of  importance  for  any  given  place,  as 
is  also  the  mean  temperature  of  the  hottest  six  weeks.  The 
annual  mean  is  frequently  computed  from  the  twelve  monthly 
means  which  is  practically  the  same  as  when  calculated 
on  the  daily  basis.  The  average  dates  of  the  last  frost  in 
spring  and  the  first  frost  in  autumn  are  also  of  great  im- 
portance to  the  pomologist  and  vegetable-gardener.  From 
these  figures  is  calculated  the  average  number  of  days  free 
from  frost  at  any  particular  point,  and  hence  the  length  of 
the  average  growing  season. 

The  total  temperature  necessaiy  for  the  development  of 
plants  or  for  the  accomplishment  of  any  phase  of  their 
growth  has  been  a  question  of  interesting  speculation  for 
many  years  and  has  resulted  in  an  attempt  to  secure  the 
"physiological  constant"  for  a  plant,  which  is  discussed  in  a 
later  paragraph.  The  general  temperature  conditions  for  the 
larger  regions  of  this  countiy  are  indicated  in  paragraph  198. 

From  the  standpoint  of  the  pollination  and  "setting" 
of  fruit,  temperature  is  of  vital  importance  and  this  is  treated 
more  fully  in  connection  with  pollination  of  fruits  (Chapter 
XII).  Aside  from  actual  injury  to  the  floral  parts,  partic- 
ularly the  pistils  from  frosts  and  low  temperatures,  the 
development  of  the  pollen-tube  may  be  checked  materially 
when  the  temperature  falls  below  50°  F.  The  bees  are  not 
active  much  below  65°  F.  and  hence  the  opportunity  for 
pollination  of  the  flowers  is  greatly  reduced  when  the  tem- 
perature remains  constantly  below  that  point  during  the 
period  of  blossoming. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    221 

191.  Rainfall. — The  rainfall  situation  is  indicated  for 
the  larger  districts  under  paragraph  199.  Most  sections  are 
likely  to  suffer  at  times  from  droughty  conditions  but  a 
large  part  of  the  United  States  is  well  supplied  with  rainfall. 
The  distribution  of  the  rainfall  throughout  the  twelve 
months  has  much  to  do  with  its  efficacy  in  crop  production, 
for  even  though  a  heavy  annual  rainfall  is  recorded  for  a 
region,  it  will  avail  little  if  a  large  proportion  of  it  falls  in 
the  non-growing  period. 

Rain  at  the  blossoming  period  of  fruit-trees  is  particularly 
injurious  to  the  crop  from  both  direct  and  indirect  causes. 
It  is  primarily  injurious  because  it  prevents  pollination,  es- 
pecially when  the  rain  is  accompanied  by  cold  weather  and 
gales  of  wind.  Injury  to  the  floral  parts  may  result  from 
such  weather  conditions,  but  more  particularly  the  insects 
instrumental  in  effecting  pollination  are  not  active.  In  the 
twenty-five  years  between  1881  to  1905,  inclusive,  Hedrick 
reports  fourteen  seasons  in  which  rain  or  snow  at  blossom 
time  was  destructive  or  partially  so  to  the  fruit  crop  in  some 
sections  of  New  York  state.  ^  The  effect  of  such  inclement 
weather  is  probably  more  pronounced  with  self-sterile 
varieties  of  fruits  than  with  the  self-fertile  ones. 

According  to  the  investigations  of  Dorsey,  rain  operates 
against  poUination  and  fruit-setting  by  causing  the  anthers 
to  close  or  by  preventing  them  from  opening,  but  it  does 
not  burst  the  pollen-grains  nor  kill  them.  Neither  does 
rain  wash  pollen  from  the  stigmas  to  any  great  extent  as 
has  been  reported,  since  there  is  a  strong  adhesive  action 
between  stigmas  and  pollen.  In  general,  however,  no  fac- 
tors of  weather  are  so  effective  in  preventing  the  setting  of 
fruit  as  rain  and  low  temperatures.- 

1  N.  Y.  (Geneva)  Agr.  Exp.  Sta.  Bull.  407.     1915. 
-Dorsey,  M.  J.     Relation  of  weather  to  fruitfulness  in  the  plum. 
Jour.  Agr.  Res.,  Vol.  17,  No.  3.     1919. 


222  POMOLOGY 

192.  Spring  frosts. — Frosts  in  autumn  are  of  some 
economic  importance  to  the  pomologist,  but  those  occurring 
in  the  spring  are  usually  much  more  disastrous  to  the  fruit 
crop,  and  are  considered  here  more  in  detail.  The  destruc- 
tion of  blossoms  and  hence  the  prospective  crop  by 
spring  frosts  either  locally  or  over  rather  large  areas  is  a 
common  occurrence  and  one  of  the  most  ruinous  phases  of 
fruit-growing. 

The  United  States  Weather  Bureau  distinguishes  three 
types  of  frost,  based  on  the  degree  or  severity  of  it,  namely: 
"light,"  "heavy,"  and  "killing."  The  latter  two  are  usu- 
ally distinguished  by  the  extent  of  injury  to  vegetation 
rather  than  to  the  actual  amount  of  deposit.  The  term 
"killing  frost"  is  described  as  one  which  is  generally  de- 
structive to  the  staple  products  of  the  locality.  Vegetation 
may  also  be  damaged  by  low  temperature  without  an  actual 
deposit  of  frost,  a  condition  due  usually  to  cloudiness.  The 
probable  dates  of  killing  frosts  for  any  locality  are  a  valu- 
able guide  to  the  fruit-grower  and  gardener  and  some  maps 
have  been  prepared  by  the  Weather  Bureau  showing  the 
dates  of  the  last  killing  frosts  in  spring  for  the  different  re- 
gions of  the  United  States.  The  same  sort  of  map  is  given 
for  the  last  killing  frosts  in  the  fall  and  for  the  average  num- 
ber of  days  without  killing  frosts.^  These  maps  are  based 
on  a  very  large  number  of  records  from  many  regular  and 
cooperative  stations  of  the  Weather  Bureau.  There  is 
great  irregularity  in  the  dates  of  the  last  frosts  in  the  spring 
and  the  first  ones  in  the  fall  for  any  given  place,  and  usually 
the  arithmetical  average  of  these  dates  is  used  in  construct- 
ing the  maps  but  such  a  date  entails  a  large  amount  of  risk, 
one  year  with  another.  On  the  other  hand,  if  the  latest 
frost  date  recorded  in  the  spring  and  the.earhest  in  the  fall 

'  Reed,  William  Gardner.  Frosts  and  the  growing  season.  U.  S. 
Dept.  Agr.  Off.  Farm  Manag.     1918. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    223 

are  used  for  calculating  crop  risks,  then  many  years  the 
grower  limits  his  season  much  more  than  would  have  been 
necessaiy. 

While  a  fruit-grower  may  attempt  to  determine  places 
that  are  safe  for  fruits  by  computing  the  average  date  of 
the  last  killing  frost,  yet  it  must  be  expected  that  in  the 
most  favorable  locations  there  will  occasionally  be  de- 
structive frosts.  For  New  York  state  Hedrick  has  recorded 
a  surprising  frequency  of  frost  damage  in  the  fruit-growing 
regions,  stating  that  "Fruits  were  injured  at  blossoming 
time  by  frosts  in  thirteen  out  of  the  twenty-five  years 
under  consideration."  ^  Frost  injuiy  may  take  the  form  of 
russeting  the  fruit,  occurring  either  in  bands,  in  patches 
about  the  basin  or  cavity,  or  in  spots  on  the  surface  of  the 
skin.  It  may  also  cause  blistering  of  the  young  leaves  when 
they  first  expand,  in  which  case  they  do  not  fully  develop 
and  often  fall  prematurely.  In  addition  to  the  destruction 
of  the  pistils  and  ovaries  of  the  flowers,  the  stems  may  be 
injured  and  the  flower-cluster  base  may  also  be  discolored, 
which  oftr>n  results  in  a  heavy  drop  of  the  fruit. 

193.  Winds. — Heavy  winds  also  play  a  part  in  the 
weather  conditions  that  affect  fruit-growing.  They  are  by 
no  means  such  destructive  agents  as  temperature  and  rain- 
fall maj^  be,  but  they  may  reduce  the  number  of  blossoms 
which  set  fruit  and  prove  ruinous  to  the  crop  as  it  approaches 
the  hai-vesting  season.  Just  as  rain  or  humid  conditions 
may  prevent  bees  and  other  pollen-carrying  insects  from 
working  during  the  blossoming  season,  so  winds  may  also 
greatly  reduce  their  activity  and  consequently  reduce  pol- 

1  N.  Y.  (Geneva)  Agr.  Exp.  Sta.  Bull.  299.  See  also  Wilson,  W.  M. 
Frosts  in  New  York.  N.  Y.  (Coniell)  Agr.  Exp.  Sta.  Bull.  31G.  1912. 
U.  S.  Dept.  Agr.  Farmers'  Bull.  1096.  1920.  Paddock,  Wendell, 
and  Orville  B.  Whipple.  Fruit-Growing  in  Arid  Regions.  New  York, 
1910. 


224  POMOLOGY 

lination.  To  what  extent  the  floral  parts,  particularly  the 
stigniatic  fluid,  of  fruits  in  general  are  affected  by  the  dry- 
ing action  of  wind  cannot  be  stated  definitely,  but  in  the 
plum  Dorsey  noted  that  dehiscence  was  quickened  as  a  re- 
sult of  wind  action  and  petals  dropped  earlier,  but  a  drying 
of  the  stigmatic  fluid  was  more  critical  late  in  the  receptive 
period  than  in  the  earlier  stage. 

The  effect  of  wind  on  the  maturing  crop  of  fruit  is  a  con- 
stant source  of  economic  loss,  as  more  or  less  fruit  is  blown 
from  the  trees  every  year  and  some  seasons  it  assumes  se- 
rious proportions.  Windbreaks  and  close  planting  of  trees  on 
the  windward  side  are  often  used  to  reduce  the  damage. 

Winds,  in  some  sections,  cause  young  trees  to  grow  one- 
sided and  to  lean  to  the  leeward,  but  it  would  be  difl^cult  to 
estimate  the  actual  damage  which  results. 

One  of  the  most  serious  effects  of  wind  in  fruit-growing 
is  that  encountered  during  the  spraying  (or  dusting)  sea- 
son. Not  infrequently  that  work  must  be  delayed  on  ac- 
count of  high  winds  until  the  fruit  crop  is  jeopardized. 

194.  Sunshine.- — Just  as  rain  is  the  most  unfavorable 
element  in  preventing  the  pollination  and  setting  of  fruit 
blossoms,  so  conversely  is  sunshine  most  favorable  to  its 
setting,  especially  when  accompanied  by  a  relatively  low 
percentage  of  humidity.  This  condition  affords  the  best 
opportunity  for  the  agencies  of  pollination  and  also  the 
growth  of  the  pollen-tube.  When  the  period  of  blossoming 
is  bright,  the  flowers  are  usually  in  bloom  for  a  shorter  period, 
as  would  be  expected.  The  absence  of  sunshine  does  not 
mean,  however,  that  pollination  may  not  take  place  freely. 
Sunlight  is  of  first  importance,  of  course,  for  the  growth  of 
plants  in  general  and  in  the  development  and  coloring  of  the 
fruit. 

195.  Hail  usually  occurs  during  the  summer  and  may 
cause  serious  loss  in  the  orchard  as  well  as  to  farm  crops. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    225 


The  hail  marks  on  the 
fruit  injure  its  selHng 
quahty  and  indeed  may 
break  open  the  skin, 
thus  encouraging  rapid 
deterioration.  In  some 
sections  it  is  not  un- 
common to  find  an 
entire  fruit  crop  de- 
stroyed.   (Fig  30). 

Serious  injury  may 
also  occur  to  the  tree 
itself,  the  healed  scars 
often  resembling  some- 
what the  work  of  the 
tree  cricket  (Oecanthus 
sp.)  or  cicada  (Tibicen 
septendecim). 

196.  Continental  ver- 
sus marine  climates. — 
The  climate  of  the  in- 
terior of  the  northern 
sections  of  the  United 
States  and  Canada  is 
nnich  more  severe  than 
is  the  marine  climate 
on  the  same  parallel. 
This  difference  is  pri- 
marily due  to  the  fact 
that  the  specific  heat 
of  water  is  much  higher 
than  the  materials  of 
which  the  earth's  sur- 


FiG.  30. — Apple  tree  injured  by  hail 
storm.  Note  abrasions  of  bark  and 
partial  defoliation. 


226  POMOLOGY 

face  is  composed.  According  to  Hann,^  if  the  specific  heats 
of  equal  weights  of  water  and  dry  soil  are  compared,  the  latter 
would  be  0.2  of  the  former,  but  when  equal  volumes  are  com- 
pared, the  specific  heat  of  the  land  is  about  O.G  that  of  water. 
In  other  words,  if  equal  quantities  of  heat  are  received  by 
equal  areas  of  land  and  of  water,  the  land  will  have  its 
temperature  increased  almost  twice  as  much  as  the  water. 
Therefore,  this  slowness  with  which  water  takes  up  and  gives 
up  its  heat  accounts  for  the  more  equable  temperature  of 
land  adjacent  to  large  bodies  of  water,  particularly  on  the 
leeward  side.  The  more  exposed  the  land  area  is  to  the 
influence  of  ocean  winds,  the  more  uniform  is  its  tempera- 
ture. 

The  case  cited  later  of  the  western  section  of  the  state  of 
Michigan  illustrates  this  fact  as  it  pertains  to  pomology. 
Just  as  marine  climates  are  more  equable,  so  continental 
climates  are  characterized  by  a  great  range  of  tempera- 
ture. 

197.  Mountain  versus  valley  climates. — One  of  the  teach- 
ings that  has  become  axiomatic  in  fruit-growing  is  to  plant 
orchards  on  elevations  and  avoid  valleys,  coves,  or  other 
places  where  the  movement  of  the  air  is  restricted.  This 
doctrine  is  based  on  the  fact  that  the  cold  air  drains  from 
the  high  lands  into  the  valleys  and  often  results  in  damage 
to  the  crops  in  the  latter  places  when  those  on  the  higher 
elevations  may  escape  injury.  Other  factors,  such  as  hu- 
midity of  the  atmosphere,  also  play  an  important  part  in  the 
behavior  of  plants  in  valleys  and  on  mountains.  In  general, 
a  climate  characterized  by  low  humidity  and  bright  sun- 
shine throughout  the  growing  season  will  usually  produce 
a  fruit  which  has  a  clear  skin  and  is  comparatively  free  from 
such  diseases  as  scab  and  sooty  fungus.     Such  a  climatic 

'  Hann,  Dr.  Julius.  Handbook  of  Climatology.  Eng.  Trans.  The 
Macmillan  Cpmpany,  New  York.    1903. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    227 

condition  usually  obtains  at  high  altitudes  and  the  reverse 
in  valleys.  High  altitudes,  especially  in  the  East,  may  be 
humid  and,  therefore,  the  greater  freedom  from  disease 
would  not  be  found  as  indicated  in  the  above  statement. 
Aside  from  the  presence  of  large  bodies  of  water,  no  factor 
is  so  potent  in  causing  differences  in  climate  along  any  par- 
allel of  latitude  as  elevation  above  sea  level. 

The  facts  here  would  seem  to  be  contradictoiy,  for  there 
is  a  vertical  decrease  of  temperature  with  the  increase  in 
elevation,  amounting  to  about  1°  F.  for  every  300  feet. 
The  amount  of  decrease  of  temperature  will  vary  with  the 
latitude,  exposure,  season,  and  local  conditions.  But 
what  is  termed  "inversions  of  temperature"  occur  in  clear 
cool  nights  up  to  a  certain  elevation  which  results  in  the 
higher  lands  being  warmer  than  the  valleys.  According  to 
Hann,^  "This  increase  of  temperature  upward  reaches  alti- 
tudes of  at  least  300  m.,  and  is  rapid  in  the  lower  strata, 
but  slower  farther  up."  In  this  country  the  effects  of  these 
inversions  of  temperature  are  experienced  at  practically  all 
elevations  at  which  fruit  is  grown,  except  as  noted  elsewhere, 
in  certain  canyons  in  the  western  United  States. 

The  occurrence  of  the  colder  temperatures  in  valleys  is 
explained  by  the  fact  that  there  is  a  radiation  of  heat  from 
the  earth  during  the  night  and  as  a  result  the  earth  is  cooled. 
The  stratum  of  air  which  lies  next  to  the  earth  is  cooled,  and, 
as  cold  air  is  heavier  than  warm,  it  results  in  its  flowing 
downward,  and  the  warmer  air  of  the  valley  rising.  Air 
will  also  lie  in  strata  of  somewhat  equal  temperatures,  which 
phenomenon  is  experienced  in  traveling  over  undulating 
country,  particularly  at  night.  As  a  result  of  the  above 
facts,  it  is  frequently  noted  that  fruit  blossoms  (and  other 
vegetation)  are  injured  or  destroyed  at  lower  elevations  and 
those  higher  up  escape  damage.  Even  the  blossoms  on  the 
1  Loc.  cit.,  p.  252. 


228  POMOLOGY 

lower  part  of  a  tree  may  be  entirely  destroyed  and  those 
above  be  unhurt  and  develop  a  crop. 

Paddock  and  Whipple  discuss  fruit-growing  at  high  alti- 
tudes as  follows:  "In  a  few  favored  locaUties  peaches  are 
successfully  grown  at  an  altitude  above  6000  feet.  But  on 
the  Eastern  slope  of  the  (Rocky)  mountains  no  peaches  are 
grown  commercially  without  winter  protection  where  the 
altitude  is  only  5000  feet.  ...  In  general  it  may  be 
said  that  as  a  rule,  fruit  cannot  be  grown  to  any  extent 
at  an  altitude  much  above  5000  feet,  and  at  this  height 
much  depends  on  the  protection  afforded  by  the  moun- 
tains." 

198.  Climate  of  United  States. — Due  to  the  extent  of 
territory  comprised  within  the  United  States,  there  is  a  great 
variety  of  climate,  from  the  Arctic  region  on  the  northwest 
to  the  semi-tropical  climate  of  the  south;  yet  the  great  pro- 
portion of  this  country  lies  within  the  temperate  zone. 
However,  as  has  been  shown  by  Henry,  ^  a  great  difference 
exists  in  the  length  of  the  growing  season  as  latitude  and  ele- 
vation are  changed  and  that  this  can  be  reduced  to  defi- 
nite laws  will  be  seen  later.  The  map  in  Fig.  31  shows  this 
variation  from  a  five  months'  season  in  the  North  to  a  twelve 
month  in  the  South.  Such  a  condition  makes  evident  that 
climate  will  limit  fruit-growing  in  certain  sections  except  as 
artificial  means  and  certain  cultural  practices  are  employed 
that  will  overcome  the  natural  barriers. 

Any  statistical  statement  of  meteorological  data  would 
be  too  extensive  for  use  here,  but  the  student  should  fa- 
miliarize himself  with  local  conditions.  The  extremes  of  rain- 
fall and  temperature  will  serve  to  emphasize  the  wide  diver- 
sity within  the  borders  of  the  United  States.  These  data 
may  best  be  examined  in  connection  with  the  several  so- 
called  climatic  provinces  of  the  United  States. 

'Henry,  A.J.    Weather  Bur.  Bull.  Q.    Washington,  D.  C.    1906. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    229 

199.  Climatic  provinces  of  the  United  States.^ — While 
chmate  frequently  vai'ies  inarkecUy  within  comparatively 
short  distances,  yet  there  are  several  grand  divisions  within 


REGIONS.  BASED    ON  PERIODS 
OF  GROWTH   AND  REST' 


Per.od  of 
Veget-ation 

■"""  V^ 

^^::^ 

SMonths 

'^^      7  Months, 

.                ^^ 

May-October.. 

6Mon(h3 

^riz'j^:'''''' 

^^^ 

Apr.l-Octobcr 
7  Months 

ipr-a  November -March 
''^      S  Months 

^* 

Apr.l-Nove  Tiber 

6  Months 

QHJ  December-March 
4Montti3 

March-November 
9  Months 

^a  December -February 
5  Months 

February  -  November  OT5i  December -Oanuary 
10  Months                       "'^     2  Months                    ' 

rebruary-Ded ember  f-r;^  January 
II  Months                        ^—^    1  Month 

January -December 

12  Months 

^  No    Period  of 
Rest 

Fig.  31.— Length  of  growing  season  in  different  parts  of  the  United 

States. 

the  country  which  represent  regions  of  similar  climate. 
These  have  been  described  as  "climatic  provinces,"  being 
five  in  number.    The  largest,  or  Eastern,  extends  from  the 

1  Adapted  from  Ward,  Robert  DeC.  The  essential  characteristics 
of  U.  S.  climates.  Sci.  Month.,  Vol.  II,  No.  6.  Dec,  1920.  See  also 
Bailey,  L.  H.  Principles  of  Fruit-Growing,  New  York.  2Cth  Ed. 
1915.     p.  11. 


230  POMOLOGY 

eastern  margin  of  the  Great  Plains,  which  roughly  coin- 
cides with  the  20-inch  annual  rainfall  line  and  also  with  the 
100th  meridian,  to  the  Atlantic  Ocean,  and  southward  nearly 
to  the  Gulf  of  Mexico.  The  strip  bordering  on  the  Gulf 
may  be  set  apart  as  a  subordinate  district,  the  Gulf  province. 
The  Plains  province  includes  the  Great  Plains  proper,  and 
extends  westward  to  the  Rocky  Mountains.  Between  the 
Rocky  Mountains  and  the  Sierra  Nevada-Cascade  ranges 
comes  the  Plateau  province.  The  Pacific  slope  constitutes 
a  natural  climatic  region  which  may  be  called  the  Pacific 
province. 

''The  differences  between  north  and  south,  resulting  from 
differences  in  latitude,  suggest  a  further  subdivision  of  the 
Plains,  Plateau,  and  Pacific  provinces  into  northern  and 
southern  sections.  Similarly,  the  Gulf  province  occupies 
the  more  southern  latitudes  of  the  Eastern  province." 

200.  The  Eastern  province. — This  extensive  area  is 
characterized  by  great  uniformity  in  its  climatic  conditions 
and  weather  types.  Over  most  of  it  the  seasons  are  strongly 
contrasted.  The  summers  are  very  warm  and  the  winters 
cold.  The  rainfall  is  abundant  or  at  least  sufficient  for  agri- 
culture and  nowhere  in  this  district  is  there  permanent  ne- 
cessity of  irrigation.  There  are  only  relatively  slight  and 
unimportant  differences  of  topography,  the  whole  area  be- 
ing freely  open  from  Canada  on  the  north  to  the  Atlantic 
Ocean  on  the  east,  and  to  the  Gulf  of  Mexico  on  the  south. 

In  January,  the  isotherms  over  the  eastern  United  States 
are  very  closely  crowded  together.  The  temperature  then 
decreases  northward  at  the  rate  of  2.7°  F.  in  each  degree  of 
latitude,  both  on  the  Atlantic  coast  and  in  the  Mississippi  Val- 
ley, which  is  an  extraordinarily  rapid  temperature-gradient. 
There  is,  however,  much  less  difference  of  temperature  be- 
tween South  and  North  in  summer.  It  becomes  1.1°  along 
the  eastern  coast  and  0.7°  in  the  Mississippi  Valley. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    231 

The  temperature  conditions  have  been  briefly  generahzed 
as  follows: 

Table  LXX 
temperature  conditions  of  the  eastern  province 


District 

Mean 
annual 

Jan. 

July 

Abs.  mux. 

Abs.  min. 

N 
S 

40° 
65°-70° 

5°-10° 
50°-55°+ 

65° 
80°+ 

100°-105° 
105° 

-40°  to —50° 
zero- 10° 

The  average  dates  of  first  and  last  frost,  broadly  gener- 
alized, are  as  follows: 

Table  LXXI 
length  of  growing  season,  eastern  province 


District 

Last  Spring 

Fii'st  Autumn 

Average  length  of 
growing  season 

N 
S 

After  June  1 

(extreme  N) 
Before  March  1 

Sept.  (extreme  N) 
November 

3-4  months 
7  months  and  over 

As  indicated  above,  the  rainfall  is  usually  sufficient  for 
vegetation  over  this  province  and  well  distributed  through- 
out the  year.  Disregarding  local  areas  on  the  mountains, 
the  amiual  rainfall  is  greatest  (50+  inches)  towards  the 
Gulf,  and  on  the  South  Atlantic  coast  and  decreases  from 
about  40-45  inches  over  much  of  the  north  and  central  Atlan- 
tic coast  and  Ohio  Valley  to  30-40  inches  over  the  prairies 
and  20  inches  at  about  the  100th  meridian. 

201.  The  Gulf  province.— Over  the  southern  tier  of 
states  bordering  on  the  Oulf  of  Mexico,  the  temperatures 
are  higher;  the  winters  are  much  milder;  the  summers  are 


232 


POMOLOGY 


longer  and  hotter;  the  rainfall  is  heavier;  and  there  is  a  late 
summer  or  early  autumn  maximum. 

202.  The  Plains  province. — The  essential  difference  be- 
tween the  climate  of  the  Great  Plains  and  that  of  the  East- 
em  province  is  not  so  much  one  of  general  temperature 
conditions  as  of  rainfall.  The  similarity  of  temperature 
may  be  seen  by  comparing  the  summary  below  with  that 
given  under  the  Eastern  province. 

Table  LXXII 
temperature  conditions  of  the  plains  province 


District 

Mean  annual 

January 

July 

Abs.  max. 

Ahs.  min. 

N 
S 

40° 

65° 

0°-10° 
40°-50° 

65°-70° 

80°-85° 

105°-110° 
110° 

—50°  to  —60° 
zero 

As  compared  with  the  eastern  states,  the  Plains  have 
larger  diurnal  ranges  of  temperature;  more  abundant  sun- 
shine; drier  air;  greater  evaporation;  smaller  rain  probabil- 
ity; less  rain;  more  wind.  The  contrast  in  rainfall  between 
the  Eastern  and  Plains  provinces  is  striking.  From  a  20-inch 
rainfall  on  the  eastern  margin  of  the  Plains,  it  decreases  to 
below  15  inches  on  the  western  margin,  and  where  the  rain- 
fall is  below  20  inches  it  is  insufficient  for  successful  agricul- 
ture, and  irrigation  must  be  practiced. 

203.  The  Plateau  province  is  a  great  interior  region  of 
very  diversified  topography.  It  has  a  wide  range  of  moun- 
tain, high  plateau,  and  arid  lowland  climate,  superposed  on 
and  causing  local  modifications  of  the  general  dry  continen- 
tal climate  of  the  province  as  a  whole.  The  outstanding 
characteristic  is  the  small  rainfall,  which,  however,  shows 
marked  increase  with  altitude.  With  the  exception  of  local 
areas  in  the  mountains,  the  mean  annual  rainfall  is  every- 
where less  than  20  inches;  it  is  mostly  below  10  inches,  and 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    233 


over  no  insignificant  portion  of  tiie  Southwest  it  is  even  be- 
low 5  inches. 

204.  The  Pacific  province. — Over  the  narrow  Pacific 
coastal  belt  climati(;  conditions  are  quite  unlike  those  else- 
where in  the  country,  and  in  many  respects  resemble  those 
of  northwestern  and  western  Europe,  including  the  Medi- 
terranean area.  The  wide  range  of  latitude  between  north 
and  south,  together  with  the  vaiying  topographic  controls 
and  the  differences  of  exposure  to  the  ocean  influences,  ex- 
plain the  great  variety  of  climate  in  this  province.  These 
range  from  those  of  the  rainy  and  densely  forested  slopes  of 
Washington  to  those  of  semi-arid  southern  California;  from 
those  of  the  lowlands  to  the  snow-covered  mountain  tops; 
from  the  cool  sununer  of  the  coast  to  the  hot  summers  of 
the  Great  Valley.  The  climate,  in  general,  is  mild  and  equa- 
ble, with  slight  diurnal  and  seasonal  ranges. 

The  following  table  summarizes,  in  a  very  general  way, 
the  essential  temperature  characteristics  of  the  Pacific  prov- 
ince: 

Table  LXXIII 


rEMPERATURE   CONDITIONS 

OF    THE    PACIFIC    PROVINCE 

District 

Mean  amiual 

Jan. 

July 

Abs.  max. 

Abs.  min. 

N 
S 

50°-55° 
65°  ± 

35°-40° 
50°-55° 

60°-65°+ 
65°-75°+ 

95°-105° 
110°-115° 

10°-  0° 
20°-10° 

The  rainfall  is  heavy  (over  100  inches)  on  the  northwest- 
em  coast  of  Washington,  and  decreases  rapidly  to  the  south, 
to  about  10  inches  in  the  San  Joaquin  Valley. 

205.  Natural  guides  to  horticultural  practices.— From 
earliest  times  the  grower  of  crops  has  made  use  of  certain 
natural  guides  to  determine  when  he  would  plant  and  har- 
vest his  crops  as  well  as  for  other  activities  about  the  farm. 
Such  an  expression  as  "it  is  time  to  plant  com  when  white 


234  POMOLOGY 

oak  leaves  are  the  size  of  squirrels'  ears"  is  familiar.  Others 
use  the  time  of  the  arrival  or  migration  of  certain  birds,  the 
unfolding  of  the  leaves  or  flowering  of  certain  plants,  or  the 
appearance  of  certain  insects  as  an  index  to  farm  and  or- 
chard practice.  Such  a  method,  if  well  observed,  should 
be  a  veiy  accurate  guide,  as  it  represents  the  sum  of  all  the 
complex  factors  involved  and  no  instrument  can  do  this. 
206.  Bioclimatic  law  of  latitude,  longitude,  and  altitude.^ — 
A  large  number  of  observations  made  at  many  points 
and  over  a  period  of  years  has  resulted  in  the  deduc- 
tion of  a  set  of  laws  in  regard  to  the  response  of  plant 
and  animal  life  to  climate.  Howard  reports  the  following 
laws: 

1.  The  periodical  phenomena  of  plants  and  animals  are 
in  response  to  the  influence  of  all  the  complex  factors  and 
elements  of  the  climate  as  controlled,  primarily,  by  the  mo- 
tions of  the  earth  and  its  position  relative  to  the  influences 
of  solar  radiation. 

2.  The  variations  in  the  climate  and  consequent  varia- 
tions in  the  geographical  distribution  and  periodical  activi- 
ties of  the  plants  and  animals  of  a  continent  are  controlled 
by  the  modifying  influences  of  topography,  oceans,  lakes, 
large  rivers,  and  of  other  regional  and  local  conditions,  and 
the  amount  and  character  of  daylight,  sunshine,  rain,  snow, 
humidity,  and  other  elements  and  factors  of  a  general  and 
local  nature. 

3.  There  is  a  tendency  toward  a  constant  rate  of  variation 
in  the  climatic  and  biological  conditions  of  a  continent  as  a 
whole  in  direct  proportion  to  variation  in  geographical  posi- 
tion as  defined  by  the  three  geographical  coordinates,  lati- 
tude, longitude,  and  altitude. 

lU.  S.  Dept.  Agr.  Monthly  Weather  Review.  Suppl.  No.  9,  1918. 
A.  D.  Hopkins.  Periodical  events  and  natural  law  as  guides  to  agricul- 
tural research  and  practice. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    235 

4.  Other  conditions  being  equal,  the  variation  in  the  time 
of  occurrence  of  a  given  periocUcal  event  in  hfe  activity  in 
temperate  North  America  is  at  the  general  average  rate  of 
4  days  to  each  1  degree  of  latitude,  5  degrees  of  longitude, 
and  400  feet  of  altitude,  later  northward,  eastward  and  up- 
ward ill  the  spring  and  early  summer,  and  the  reverse  in 
late  suimiier  and  autumn. 

5.  Owing  to  the  fact  that  all  conditions  are  never  exactly 
equal  in  two  or  more  biological  or  climatic  regions  of  the 
continent,  and  rarely  alike  in  two  or  more  places  within  the 
same  region  or  locality,  there  are  always  departures  from 
the  theoretical  time  constant. 

6.  The  departures,  in  number  of  days  from  a  theoretical 
time  constant,  are  in  direct  relation  to  the  intensity  of  the 
controlling  influences.  Therefore,  the  constant,  as  expressed 
in  the  time  coordinates  of  the  law,  is  a  measure  of  the  inten- 
sity of  the  influences. 

Fig.  32  shows  the  working  of  this  law  as  adapted  to  North 
America.  "Taking  base  maps  of  North  America  and  of 
the  major  and  minor  political  divisions,  parallel  lines  (des- 
ignated as  isophanes  ^)  are  drawn  on  them  to  define,  accord- 
ing to  the  bioclimatic  law,  theoretical  lines  and  zones  of 
equal  phenomena  as  to  time  of  occurrence  and  equal  biocli- 
matic conditions,  at  the  same  level."- 

"The  isophanes,  instead  of  following  the  parallels  of 
north  latitude  in  North  America,  proceed  from  the  Atlan- 
tic to  the  Pacific  in  a  northwestward  curve  at  the  rate  of  1 
degree  of  latitude  to  5  degrees  of  longitude  (Fig.  32),  so 

*  Isophane.  In  phenology,  an  isochrone  of  the  first  blossoming  of 
a  specified  plant. 

Isochrone.  Phenological  isochrone  is  a  line  drawn  between  points 
at  which  plants  of  the  same  species  attain  the  same  degree  of  de- 
velopment simultaneously.     (Standard  Dictionary.) 

^  For  full  explanation,  see  original  text. 


23G 


POMOLOGY 


that  they  serve  as  a  diagrammatic  expression  of  the  average 
rate  of  four  days'  variation  for  1  degree  of  latitude  and  5 


Fig.  32. — Isophanal  map  of  North  America. 

degrees  of  longitude.     Therefore  one  of  these  lines  across  the 
continent  at  any  given  level  of  land  surface  represents  the 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    237 

same  average  phenological  constant  date  of  a  seasonal  event 
and  the  same  average  climatic  and  biological  conditions." 

In  other  words,  if  1  degree  of  latitude  is  assumed  to  be 
equal  to  about  70  miles  and  1  degree  of  longitude  equal  to 
50  miles,  then,  other  things  being  equal,  there  are  4  days 
variation  for  eveiy  70  miles  north  or  south  and  for  every 
250  miles  east  or  west  from  a  given  point,  and  for  every 
400  feet  altitude.  Or  if  any  given  isophane  is  followed, 
there  would  be  no  variation  in  time  of  occurrence  of  the  nat- 
ural phenomena.  Variations  from  these  rules  will  occur, 
depending  on  such  modifying  influences  as  are  mentioned 
in  rule  2. 

A  fuller  appreciation  of  this  subject  means  that  spray  cal- 
endars must  be  made  up  for  conditions  of  similar  climatic 
conditions;  a  study  of  insect  and  disease  control  must  con- 
sider the  local  conditions;  and  so  for  many  agricultural  prac- 
tices and   researches. 

207.  Species  adaptation. — It  is  not  a  settled  question 
as  to  liow  far  a  species  native  to  one  set  of  climatic  condi- 
tions can  become  adapted  to  an  entirely  different  climate. 
That  is,  can  a  plant  from  a  warm  region  gradually  become 
acclimated  to  a  cold  one  and  hence  secure  hardier  strains 
or  races  of  tender  plants?  Can  a  plant  which  requires  a 
moist  growing  season  gradually  become  adapted  to  xero- 
phytic  conditions  or  vice  versa?  These  questions  are  of  great 
importance  in  the  science  of  pomology  and  much  difference 
of  opinion  is  recorded  in  literature.  It  is  now  usually  ac- 
cepted, however,  that  a  plant  is  not  gradually  changed  to 
suit  its  enviroimient  but  that  it  is  necessaiy  to  secure  indi- 
viduals which  possess  the  character  desired  and  from  this 
stock  so  breed  a  new  strain  as  to  combine  other  desirable 
qualities.  At  least  this  would  seem  to  be  the  shortest  and 
surest  method  of  securing  better  fruits  for  extreme  condi- 
tions of  soil  and  climate. 


238 


POMOLOGY 


It  is,  of  course,  well  known  that  a  given  variety  or  species 
becomes  somewhat  adapted  to  the  length  of  growing  sea- 
son in  widely  differing  sections  of  the  country,  but  this  is 
not  to  be  interpreted  as  meaning  that  a  variety  of  peach, 
apple,  or  other  fruit  having  the  capacity  to  withstand  a  cer- 
tain minimum  degree  of  temperature  may  be  acclimated  to  a 
still  lower  one  by  adaptation.  The  work  of  Whitten,  Dorsey, 
Macoun,  and  others  show  adaptation  within  certain  limits. 

208.  Temperatures  which  injure  setting  of  fruits. — It  is 
well  known,  as  stated  above,  that  frosts  destroy  fruit  blos- 
soms frequently,  but  it  is  also  true  that  injury  may  occur 
without  apparently  killing  the  tender  tissues.  The  after 
effects  of  the  latter  are  seen  in  the  heavy  fall  of  fruit  during 
about  three  weeks  following  the  blossom  period. 

The  following  figures  give  the  temperatures  at  which  the 
various  fruits  may  be  injured  at  blossom  time: 


Table  LXXIV 
temperatures  which  injure  setting  of  fruits  ^ 

Fruits 

In  bud 

In  blossom 

In 

selling  fruit 

Degrees  F 

Degrees  F 

Degrees  F 

Almonds 

28 
27 
30 
22-29 
31 
29 
28 
30 
28 
28 
28 

30 
29 
31 
28-30 
31 
30 
29 
31 
28 
28 
28 

30 

30 

Apricots 

Cherries 

Grapes 

Peaches 

Pears 

Plums 

Strawberries 

Raspberries 

32 
28-30 
30 
30 
29 
31 
28 
28 

Blackberries 

28 

'  See  West,  Frank  L.,  and  N.  E.  Edlefsen.    Freezing  of  fruit  buds. 
Jour.  Agr.  Res.,  Vol.  20,  No.  8.    1921. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    239 

Several  factors  determine  at  what  temperature  such  in- 
jury occurs,  for  it  is  well  known  that  it  is  not  consistent. 
The  amount  of  moisture  in  the  atmosphere  at  the  time  of 
frost  is  conmionly  cited  as  of  the  greatest  importance,  the 
greater  tlic  humidity  the  less  likely  will  there  be  injuiy.  Also 
the  individuality  of  the  plant  may  enter  into  the  problem. 

West  and  Edlefsen  conmient  as  follows  in  regard  to  this 
phenomenon:  "The  fact  that  the  same  branch  of  buds  will 
on  one  occasion  experience  27°  F.  with  25  per  cent  injuiy 
and  on  another  occasion  take  the  same  temperature  with 
no  injuiy  is  no  doubt  due  to  the  fact  that  the  juice  is  con- 
tained in  capillaiy  cells  and  supercooling  results — that  is, 
the  buds  are  cooled  below  the  freezing  point  of  the  juice 
without  the  freezing  taking  place.  The  great  difficulty  of 
killing  all  the  buds  even  at  extremely  low  temperatures  is 
due  to  the  same  cause  together  with  the  fact  that  the  cell 
sap  may  be  very  concentrated.  Differences  in  the  hardi- 
ness of  the  different  kinds  of  buds  and  also  of  the  same  buds 
at  different  stages  of  development  is  due  to  differences  in 
quality  and  concentration  of  the  cell  sap." 

It  is  easy  to  overestimate  the  damage  at  the  time  of  the 
low  temperatures,  for  no  means  are  available  for  determin- 
ing the  extent  of  injuiy  unless  the  floral  parts  (usually  the 
pistils  first)  are  blackened  or  withered.  Orchards  in  which 
the  blossoms  seemed  entirely  destroyed  may  still  set  a  fair 
crop  of  fruit. 

209.  Averting  injury  from  frosts  and  freezes.^ — Attempts 
are  sometimes  made  to  avert  injuiy  to  the  fruit  crop  from 
spring  frosts  by  various  devices.  Whitten  ^  whitewashed 
peach  trees  to  delay  their  blossoming,  with  some  success. 
The  principle  made  use  of  here  is  that  a  white  surface  will 

'  See  papers  on  frosts  and  frost  protection  in  U.  S.    U.  S.  Dept.  Agr. 
The  Monthly  Weather  Review,  42:  562-592.     1914. 
2  Mo.  Agr.  Exp.  Sta.  Bull.  38.     1897. 


240  POMOLOGY 

reflect  light  and  heat,  while  a  dark  one  absorbs  it.  Thus 
the  whitewashed  trees  were  delayed  a  few  days  in  their  time 
of  blooming.  He  also  shifted  the  resting  period  later  in  the 
winter  by  later  tillage  and  accomplished  similar  results. 

The  heating  and  smudging  of  orchards  are  also  used 
rather  extensively  in  some  sections  to  ward  off  frosts  and  hold 
the  heat  radiated  from  the  earth. 

Laying  trees  and  vines  down  during  the  winter  and  cov- 
ering with  earth  or  other  material  is  also  practiced  to  a  lim- 
ited extent,  as  well  as  baling  trees  up  with  straw  or  fodder. 

The  important  factor  here,  however,  is  the  proper  loca- 
tion of  the  orchard.  As  indicated  previously,  high  lands 
are  more  immune  to  frosts  than  low  ones,  so  that  there  is  a 
free  movement  of  air  and  a  drain  of  the  cold  air  to  lower 
levels;  also  coves  or  pockets  should  be  avoided.  The  slope 
of  the  land  is  of  some  importance,  particularly  as  the  south- 
ern limits  of  fruit-growing  are  approached,  and  also  with 
fruits  that  respond  quickly  to  warm  spells  of  weather  oc- 
curring early  in  the  season.  The  southern  and  southeastern 
slopes  absorb  more  heat  and  hence  trees  often  blossom  some- 
what earlier  here  than  on  the  northern  exposures.  It  is  easy 
to  overestimate  the  value  that  can  be  gained  by  such  a 
selection,  however. 

The  following  figures  indicate  the  proportional  amount 
of  heat  received  to  a  unit  area  by  different  slopes  on  June 
21,  at  the  42d  parallel  north  latitude:^ 

20°  Southerly  slope  =  106 

Level  =  100 

20°  Northerly  slope  =    81 

One  of  the  best  known  and  in  some  respects  most  unique 
cases  of  the  effect  of  water  on  climate  is  seen  in  the  Michi- 
gan "fruit-belt."    This  is  a  strip  of  land  from  ten  to  twenty 

1  After  Lyon,  Fippin,  and  Buckman.  Soils.  New  York.  1915.    p.  318. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    241 

miles  in  width  along  the  west  side  of  the  state  from  the  In- 
diana line  nearly  to  the  Straits  of  Mackinaw.  The  southern 
boundary  of  this  belt  is  about  42°  N.  latitude  while  the 

i        jL..^  J    DELTA 


Fig.  33. — Map  showing  the  boundaries  of  the  Michigan  fruit-belt. 


northern  boundary  is  almost  46°,  and  in  this  belt  are  exten- 
sively grown  such  tender  fruits  as  the  peach  and  cherry. 
The  accompanying  map  ^   (Fig.  33)   shows  the  boundaries 

1  After  Seely,  adapted  from  Taft.    Commercial  cherry  culture.    Proc. 
Amer.  Pom.  Soc.  1917.    p.  107. 


242  POMOLOGY 

of  the  fruit-belt  and  indicates  the  isothermal  lines  as  they 
locate  the  last  killing  frosts  of  the  spring.  The  tempered 
effect  along  this  littoral  region  is  due  to  the  prevailing  winds 
passing  over  Lake  Michigan  during  most  of  the  winter  and 
spring  months.  In  the  spring  the  winds  are  kept  continually 
cool  in  passing  over  the  lakes  and  hence  prevent  unseason- 
able advancement  of  the  fruit-buds  in  April  and  May 
which  results  in  disastrous  effects  in  unprotected  regions. 
On  the  other  hand,  the  winter  winds  that  leave  the  Wiscon- 
sin shore  at  a  temperature  of  thirty  to  forty  degrees  below 
zero  arrive  on  the  Michigan  side  at  a  temperature  of  little 
if  any  below  zero,  since  the  waters  of  the  lake  rarely  freeze 
over  and  are  connnonly  some  three  to  five  degrees  above 
the  freezing  point.  While  a  minimum  range  of  ten  to  fifteen 
degrees  below  zero  may  be  recorded  along  the  northern  sec- 
tion of  this  "belt,"  it  may  be  thirty  or  forty  degrees  below 
zero  in  the  north-central  counties  of  the  state. 

210.  Effect  of  climate  on  the  floral  structure. — Climate 
may  have  a  veiy  definite  effect  on  the  floral  structure  and 
more  particularly  on  the  vitality  of  the  parts  of  the  flower. 
A  long  and  serious  controversy  was  waged  in  the  early  his- 
tory of  strawberiy-growing  in  this  country  (1850-70)  on 
the  sexual  characters  of  this  fruit.  In  some  sections  cer- 
tain varieties  were  perfect  flowering  and  in  others  the  same 
kinds  were  imperfect.  That  the  climate  had  affected  them 
in  this  way  was  later  discovered.  The  same  is  true  with 
the  strawberry  grown  in  eastern  United  States  and  in  Eng- 
land, where  in  the  latter  place  the  mild,  humid  climate  some- 
times causes  imperfect  flowering  sorts  to  become  perfect. 

The  Bartlett  pear,  which  is  usually  self-sterile,  is  reported 
by  Garcia  to  be  sufficiently  self-fertile  to  insure  fair  crops 
of  fruit  in  New  Mexico.  Likewise  in  California  it  was  found 
that  the  Bartlett  is  self-sterile  on  the  high  elevations  and 
partially  self-fertile  in  the  valleys. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    243 

211.  The  effect  of  climate  on  development  of  fruit. — 

Shaw  ^  luis  shown  that  the  variation  in  apple  varieties  is 
due  to  three  principal  causes:  (1)  cultural  practices,  (2)  soil 
variation,  (3)  climate.  Of  the  climatic  influences,  he  places 
temperature  as  the  most  potent. 

From  his  researches  he  draws  the  following  significant 
conclusions:  (1)  "Variation  in  form  in  the  Ben  Davis,  and 
probabl}^  in  other  sorts  as  well,  is  due  principally  to  the  tem- 
peratm-e  during  a  period  of  about  two  or  three  weeks  fol- 
lowing blossoming.  The  lower  the  temperature  the  more 
elongated  the  apple.  This  elongation  is  seen  in  apples  grown 
near  large  bodies  of  water,  which  lower  the  temperature  at 
this  season  of  the  year,  and  in  seasons  where  the  tempera- 
ture is  low  owing  to  seasonal  fluctations.  This  influence 
is  also  seen  in  the  form  of  apples  in  different  parts  of  the 
tree.  Those  in  the  lower  north  portion  are  more  elongated 
than  those  from  the  warmer,  upper  south  portion. "  (2)  "  Sea- 
sonal temperature  affects  the  size  of  apples,  a  cool  season 
resulting  in  smaller  fruit.  This  is  marked  only  in  full  sea- 
son varieties,  and  is  especially  noticeable  in  the  more  north- 
erly portions  of  their  distribution.  On  the  other  hand,  in 
the  extreme  south  a  variety  is  apt  to  be  smaller  than  when 
grown  in  a  somewhat  cooler  climate." 

212.  Climatic  factors  which  delimit  the  geographical 
distribution  of  fruits. — As  pointed  out  earlier  in  the  chap- 
ter, climatic  factors  limit  the  growing  of  deciduous  fruits  as 
the  northern  and  southern  boundaries  of  the  temperate 
zone  are  approached.  These  factors  are  defined  by  Shaw  as 
follows:  "The  northern  limit  of  apple-growing  is  fixed  by 
the  minimum  winter  temperature,  and  the  southern  limit 
by  the  heat  of  the  hottest  part  of  summer,  occurring  usually 
in  July  or  August. 

"The  attainment  of  the  highest  quality,  appearance  and 
1  Mass.  Agr.  Exp.  Sta.    22nd  Ann.  Rept.  1910.    23rd  Ann.  Rept.  1911. 


244  POMOLOGY 

keeping  quality  is  very  largely  dependent  on  the  warmth 
and  length  of  the  growing  season.  This  may  be  measured 
with  fair  satisfaction  for  the  apple-growing  regions  of 
North  America  by  an  average  of  the  mean  temperatures 
for  the  months  of  March  to  September,  inclusive.  This  is 
called  the  mean  summer  temperature,  and  gives  tempera- 
tures ranging  from  52°  to  72°  F. 

"The  factors  determining  the  mean  suimner  temperature 
in  a  given  orchard  are  (1)  latitude,  (2)  elevation,  (3)  site 
and  aspect,  (4)  soil,  (5)  culture,  (6)  prevailing  winds,  (7) 
sunshine. 

''A  departure  of  over  2°  from  the  optimum  mean  for  a  given 
variety  will  result  in  less  desirable  fruit,  though  this  may 
not  be  marked  in  short  season  varieties. 

"A  summer  mean  too  low  for  a  variety  results  in  (1) 
greater  acidity,  (2)  increased  insoluble  solids,  (3)  greater 
astringency,  (4)  less  coloration,  (5)  decreased  size,  (6) 
scalding  in  storage. 

"A  summer  mean  too  high  for  a  variety  results  in  (1) 
uneven  ripening,  (2)  premature  dropping,  (3)  rotting  on 
the  trees,  (4)  poor  keeping  quality,  (5)  lack  of  flavor,  (6) 
'mealiness,'  (7)  less  intense  color,  (8)  decreased  size." 

213.  Specific  requirements  for  certain  varieties.^ — It 
seems  to  be  established,  as  above  stated,  that  a  variet}^  of 
fruit  has  a  certain  optimum  temperature  at  which  it  thrives 
best,  but  this  has  not  been  determined  for  all  varieties.  Win- 
slow  ^  has  contributed  some  interesting  figures  on  the  length 
of  growing  season  required  by  some  varieties  of  apples 
grown  in  the  Northwest.  The  "length  of  growing  season" 
is  described  by  him  as  the  number  of  days  between  killing 
frosts,  or  more  accurately  the  period  during  which  the  mean 
temperature  is  over  43°  F.  He  also  uses  the  number  of 
"heat  units"  during  the  growing  season  as  a  guide  in  the 
1  Winslow,  R.  M.    Amer.  Soc.  Hort.  Sci.    1914. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    245 

selection  of  a  suitable  location  for  the  different  varieties. 
The  heat  units  for  each  month  are  determined  by  multipl}^- 
ing  the  number  of  days  in  the  month  by  the  mean  monthl}' 
temperature.  In  this  way,  the  sum  total  of  heat  during  the 
season  is  expressed  in  heat  units  or  given  an  index.  The 
"hottest  six  weeks"  are  also  made  use  of,  since  this  period  is 
considered  a  guide  to  the    intensity  of  the  summer  heat.' 

Such  varieties  of  apples  as  the  Yellow  Newtown  and  Esopus 
(Spitzenburg)  are  conspicuously  limited  in  their  range  of 
successful  production.  In  only  a  few  localities  are  they  at 
their  best,  while  in  other  places  well  adapted  to  many  va- 
rieties these  two  are  of  low  quality  and  unreliable  in  their 
behavior.  Winslow  shows  that  the  Yellow  Newtown  requires 
a  climate  possessing  a  long  growing  season,  a  high  mean 
summer  temperature,  a  high  total  of  heat  units  for  the  sea- 
son, and  it  prefers  a  humid  district  where  irrigation,  if 
needed  at  all,  is  only  supplementary.  It  is  pointed  out  that 
other  districts  having  similar  conditions  are  adapted  to  the 
production  of  this  variety,  but  if  they  depart  much  from 
them,  the  results  are  unsatisfactory. 

The  Esopus  is  similar  in  its  climatic  requirements  to  the 
Yellow  Newtown,  with  the  exception  that  irrigation  sec- 
tions are  equally  well  adapted  to  its  culture. 

Likewise  the  Winesap,  which  is  at  its  best  in  compara- 
tively few  sections,  such  as  the  Piedmont  region  of  Virginia 
and  the  Wenatchee  and  Yakima  valleys  of  Washington,  re- 

^  See  also  Merriam,  C.  H.  Laws  of  temperature  control  of  the  geo- 
graphic distribution  of  terrestrial  animals  and  plants.  Nat.  Geogr. 
Mag.,  VI,  1894,  220-238.  The  formula  used  for  determining  the  hottest 
six  weeks  is:  "multiply  the  monthly  mean  temperature  of  the  hottest 
month  by  3,  add  the  mean  temperature  of  the  next  hottest  month  and 
divide  the  total  by  4."    Example:  If  August  monthly  mean  temperature 

is  68°  and  July  66°,  then:  — ^— =  67.5°  temperature  of  the  six 

hottest  weeks. 


246 


POMOLOGY 


quires  a  long  growing  season  witli  a  high  summer  tempera- 
ture. SHght  departures  from  these  requirements  are  at 
once  manifest  in  a  smaller  size  and  poorer  color. 

Figures  for  these  more  conspicuous  examples  are  quoted: 


Table  LXXV 


LENGTH    OF    GROWING    SEASON    FOR    YELLOW    NEWTOWN,    ESOPUS,    AND 
WINESAP    APPLES     (AFTER    WINSLOW) 


Length  of 
grouring 
season 

Total 
heat  units 

Hottest 
six  weeks 

Yellow  Newtown 

days 
240  270 

13,750-15,700 

F. 

67.5°-70.7° 

irrigated  sections 

Winesap 

230-240 

13  700 

70.7° 

PHENOLOGICAL  STUDIES 

The  student  will  find  a  profitable  field  of  study  in  observ- 
ing the  relation  between  climate  and  certain  periodic  phe- 
nomena of  fruit-trees,  such  as  time  of  blooming  and  ripening 
of  fruits. 

214.  The  physiological  constant.^ — There  have  been  a 
number  of  attempts  to  calculate  the  total  amount  of  heat 
or  temperature  necessary  for  a  plant  to  function    and  go 

iWaugh,  F.  A.  Vt.  Agr.  Exp.  Sta.  11th  Ann.  Kept.  1897-98. 
pp.  263-272. 

I.  Lamb,  G.  N.  A  calendar  of  the  leafing,  flowering,  and  seeding  of 
the  common  trees  of  the  Eastern  U.  S. 

II.  Smith,  J.  Warren.  Phenological  dates  and  meterological  data 
recorded  by  Thomas  Mikesell  between  1873  and  1912  at  Wauseon, 
Ohio.    U.  S.  Dept.  Agr.  Weather  Bur.  Suppl.  2.     1915. 


I   '  ■';  -J. 


V/ 


.iruViy>"tt.''^'srqBiiwwawg^' 


Plate  VI. — In  the  background  is  shown  the  effect  of  acid  pliospliate 
on  the  natural  growth  of  clover  in  the  Ohio  experiments. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    247 

through  its  natural  phenomena,  such  as  blossoming,  putting 
out  leaves,  and  the  like.  The  formulation  of  such  laws  is 
not  surprising,  and  they  were  at  first  widely  accepted ;  how- 
ever, there  are  several  fundamental  objections  to  them. 

Hoffmann  suggested  that  the  time  of  bloom,  as  well  as  the 
other  natural  phenomena  in  the  seasonal  development  of 
the  tree,  is  dependent  on  the  sum  total  of  heat  available  to 
the  plant  up  to  that  event.  His  zero  point  was  arbitrarily 
fixed  at  the  first  of  January  after  which  he  took  the  sum  of 
the  daily  maximum  positive  temperatures  (above  32°  F.) 
of  a  thermometer  exposed  to  the  sun  up  to  the  beginning 
of  the  event.  In  this  way,  he  accounted  to  a  large  extent  for 
the  difference  in  time  of  blooming  of  different  seasons. 

De  CandoUe  and  others  have  fixed  the  temperature  at 
which  the  plant  becomes  active  at  43°  F.  (6°  C.)  instead  of 
32°  F.,  but  even  this  ignores  the  well-established  fact  that 
plants  have  different  optimum  temperatures.  It  also  may 
be  assumed  that  the  separate  phases  of  the  plant  activities 
may  have  different  optima. 

Furthermore,  it  has  been  pointed  out  that  the  buds  of  the 
tree  may  be  much  further  advanced  when  they  enter  the 
winter  condition  some  seasons  than  others,  due  to  the  sea- 
sonal variations.  This  would  probably  modify  the  total 
amount  of  heat  necessaiy  for  blossoming  the  ensuing  sea- 
son. Hence,  it  seems  impractical  to  lay  down  any  physio- 
logical constant  for  plants. 

215.  The  blooming  season. — As  indicated  above,  fruit- 
trees  of  any  given  variety  do  not  bloom  at  exactly  the  same 
time  year  after  year,  but  may  be  a  few  days  earlier  or  later 
than  the  average,  depending  largely  on  the  character  of  the 
season.  In  an  "early"  season,  they  will  bloom  earlier  and 
in  a  later  season  the  blooming  will  be  retarded.  In  addition 
to  the  total  temperature  available,  other  factors  must  also 
play  a  part  in  causing  the  difference,  such  as  the  intensity  of 


248  POMOLOGY 

heat  at  any  given  time  in  causing  the  blossoms  to  open;  the 
age  and  vigor  of  the  trees;  the  moisture  factor;  and  also  the 
character  of  the  previous  season  and  winter.  Also  winter- 
injured  buds,  if  not  entirely  killed,  are  likely  to  open  later 
than  normal  ones.  Hedrick  also  points  out  that  "In  some 
seasons  a  species  or  variety  may  bloom  a  little  before  leaves 
burst  forth;  in  others,  leaf  and  flower  come  out  simultane- 
ously and  in  still  others  leafing  precedes  blooming.  In  south- 
ern climates  the  tendency  in  several  fruits  is  to  bloom  before 
they  leaf,  while  in  the  north  the  same  fruit  will  leaf  and 
bloom  together  with  the  first  wave  of  summer  weather." 
He  also  states  that  varieties  of  hardy  fruits  vary  in  the  rel- 
ative time  at  which  they  bloom.  Some  seasons  one  variety 
will  bloom  first  and  another  year  the  order  is  reversed. 

As  pointed  out  previously,  the  location  has  a  definite  in- 
fluence on  blooming  time,  as  proximity  to  large  bodies  of 
water  which  retard  the  blooming  on  the  leeward  side  of  such 
water;  the  slope  of  a  hill  which  manifests  a  difference  in 
temperature  in  the  early  season;  and  lastly  but  most  impor- 
tant, the  latitude  and  altitude. 

216.  Comparative  blooming  dates. — In  order  to  com- 
pare the  relative  time  at  which  the  several  fruits  are  most 
likely  to  begin  to  bloom,  the  following  figures  for  New  York 
state  may  be  cited  :^ 

1  See  also  Utah  Agr.  Exp.  Sta.  Bull.  128.  1913.  Vt.  Agr.  Exp.  Sta., 
nth  Ann.  Kept.  1897-98.  pi^.  248-2.57.  Jour.  Royal  Hort.  Soc.  36: 
548-564.     1910-11.    37:350-361.    1911-12. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    249 


Table  LXXVI 

VE   DATES  OP  BLOOM  OF  THE 

MORE  COMMOl 

Sweet  cherries 

May  1 

Pears 

May  2 

European  plums 

Japanese  pluma 

Hybrid  pluma 

May  3 

Currants 

Apples 

Sour  cherries 

May  4  ' 

Hybrid  cherries 

Gooseberries 

Peaches 

May  5 

Crab-apples 

May  6 

Native  plums 

May? 

Strawberries 

May  16 

Blackberries 

Dewberries 

May  31 

Black  raspberries 

Red  raspberries 

June  1 

Hybrid  raspberries 

June  7 

Grapes 

June  14 

217,  Duration  of  blooming  period. — It  is  a  common  ob- 
servation that  fruit-trees  are  in  blossom  longer  some  seasons 
than  others.  This  is  due  to  the  weather  conditions  at  the 
time  of  bloom,  cold  and  damp  prolonging  the  period  of  flores- 
cence and  bright  sunny  days  reducing  it.  The  following 
data  ^  will  serve  to  illustrate  this : 

1  N.  Y.  Agr.  Exp.  Sta.  Bull.  407.  See  also  Vt.  Agr.  Exp.  Sta.,  11th 
Ann.  Rept.  1897-98.     p.  250. 


250 


POMOLOGY 


Table  LXXVII 


BLOOMING  RECORDS  FOR  PERIOD  OF  THREE  TO  FIVE  YEARS  AT 
GENEVA,   N.    Y.  (AFTER  HEDRICK) 


Ave.  period 
of  bloom 

Shortest 
period 

Longest 
period 

12 

7 

18 

Pears 

10 

5 

15 

Peaches 

10 

6 

16 

6 

4 

8 

8 

5 

11 

Grapes 

20 

19 

21 

European  plums 

Varieties    vary    greatly,    from 

middle  of  April  to  second  week 
in  May;  in  bloom  from  one  to 
three  weeks 

Salicina  plums 

In  bloom  from  4  to  8  days 

Native  plums 

Season  the  latter  part  of  that 
of  Domesticas 

Gooseberries 

10 

9 

12 

8 

7 

9 

24 

20 

27 

Red,  yellow,  and  hybrid  raspberries .  , . 

14 

14 

15 

Black  raspberries 

7 

6 

9 

Strawberries 

17 

11 

26 

THE  RELATION  OF  CLIMATE  TO  POMOLOGY    251 

218.  Period  of  ripening  of  hardy  fruits. — A  distinction 
must  be  made  between  tlie  time  when  winter  fruit  is  picked 
from  the  tree  and  when  it  is  "eating  ripe."  This  difference 
does  not  obtain  for  summer  varieties  of  fruit,  for  they  are 
usually  ready  to  use  at  the  time  of  picking.  The  earlier 
fruits  also  are  likely  to  show  a  variation  in  time  of  maturity 
which  may  necessitate  several  pickings.  The  same  hypoth- 
esis considered  under  blossoming  has  also  been  applied  to 
ripening  of  fruit,  namely,  Hoffman's  theoiy  of  a  thermal 
constant.  Here  again  latitude,  soil,  and  site  are  all  factors 
that  influence  the  ripening  period. 

An  extensive  list  of  the  common  fruits  has  been  prepared 
by  Hedrick  *  which  gives  the  time  of  ripening  of  each. 

219.  Relation  between  blooming  and  ripening. — Whether 
there  is  a  correlation  betw{>en  time  of  blooming  and  ripening 
is  a  question  of  considerable  practical  as  well  as  academic 
importance  and  several  conflicting  views  have  been  held  in 
regard  to  it.  The  large  amount  of  data  collected  by  Hedrick 
permits  a  general  statement,  although  many  exceptions  may 
be  cited.  He  says,  "It  requires  only  a  cursory  comparison 
of  the  data  in  the  two  bulletins  to  show  that  there  are  no 
correlations  between  blooming  time  and  ripening  time  of 
fruits." 

From  data  secured  from  Hedrick 's  "Peaches  of  New  York," 
Norton  ^  has  prepared  the  following  table,  which  shows 
lack  of  a  definite  correlation: 

1  N.  Y.  Agr.  Exp.  Sta.  Bull.  408.     1915. 

2  Norton,  J.  B.  S.    Proc.  Amer.  Soc.  Hort.  Sci.    1918. 


252 


POMOLOGY 


Table  LXXVIII 
relation  op  the  blooming  and  ripening  period  of  the  peach 


Ripening  period 

Blooming  'period 

Very 
early 

Early 

Medium 

Late 

Very 
late 

Total 

0 

0 

1 

0 

0 

1 

Early 

3 

4 

13 

3 

2 

25 

Medium .    .          .        . 

3 

15 

53 

43 

15 

129 

Late 

1 

1 

6 

7 

5 

20 

Very  late 

0 

0 

1 

1 

2 

4 

Totals 

7 

20 

74 

54 

24 

179 

220.  Form  for  recording  phenological  data. — The  fol- 
lowing form  is  recommended  by  Hopkins  ^  as  adapted  to 
the  use  of  the  orchardist  for  recording  phenological  data: 


Phenological  records 

Year.  . 

Locality 

Latitude. or  isophane 

Station  No. 

Species:  Pyrus  Mains 

County 

Longitude  or  pheno-meridian 

Observer 

Common  name:  Apple 

State 
Altitude 
Slope 

Species,  variety,  or  number 

a 

b 

c 

d 

e 

f 

9 

h       i 

Ben  Davis 

Grimes  Golden 

.  .  .  . 

Lac.  cit. 


THE  RELATION  OF  CLIMATE  TO  POMOLOGY    253 

The  spaces  with  letters  a  to  i  for  the  name  or  designa- 
tion of  the  seasonal  events  as  given  in  the  following  lists  for 
the  different  types  of  plants,  and  the  blank  spaces  below 
the  designated  events  are  for  the  date  of  occurrence. 

a.  First  buds  opening. 

b.  First  leaves  unfolding. 

c.  First  flowers  open. 

d.  First  flowers  falling. 

e.  First  winter-buds  forming. 

f.  First  seed  or  ripe  fruit. 

g.  First  leaves  coloring, 
h.     First  leaves  falling. 
i.     Other  data. 


CHAPTER  XI 
WINTER  INJURY 

For  convenience,  the  kinds  of  winter  injury  to  fruit-trees 
may  be  grouped  into  three  general  classes:  (1)  bud  injury, 
(2)  injury  of  the  woody  parts  above  ground,  and  (3)  root 
injury. 

221.  Bud  injury. — While  many  factors  are  involved  in 
winter-killing  of  plants  or  their  parts,  the  conditions  under 
which  the  buds  are  killed  may  be  roughly  placed  in  the  three 
following  categories:  (1)  when  buds  go  into  the  winter  in 
an  innnature  condition  and  low  temperatures  occur  early 
in  the  winter  (December);  (2)  when  mature  buds  are  sub- 
jected to  such  low  temperatures  during  the  winter  that 
their  tissues  are  killed;  and  (3)  when  unseasonably  warm 
weather  in  winter  or  early  spring  is  followed  by  very  low 
temperature. 

Of  the  tissues  of  the  fruit-buds  the  pistils  and  ovaries  are 
the  most  tender  and  are  frequently  killed  when  the  other 
parts  remain  unhurt.  Such  blossoms  may  expand,  espe- 
cially'if  the  injury  occurs  just  prior  to  blossoming  time,  but 
of  course  they  can  produce  no  fruit.  ^  If  the  entire  bud  is 
killed,  the  tissues  throughout  turn  brown  and  the  bud  dries 
and  falls  from  the  tree  in  the  spring  in  the  case  of  most  of 
the  stone-fruits,  or  it  may  persist  for  a  time  with  the 
apple  and  pear  as  shown  in  Plate  VIII  a. 

Not  all  varieties  of  fruit  that  are  tender  in  the  bud  are  also 
tender  in  wood,  as  may  be  illustrated  by  the  Elberta  peach, 
but  generally  this  is  true. 

Winter-killing  of  the  fniit-buds  of  the  apple  is  rare,  but 
1  Bailey,  L.  H.    Principles  of  Fruit-Growing.  20th  Ed.    p.  306. 
254 


WINTER  INJURY 


255 


has  been  reported  by  Whipple  ^  as  occurring  in  Montana.  In 
such  cases,  the  axiUaiy  leaf-bud  will  continue  the  growth 
of  the  spur  and,  before  the  growing  season  is  over,  it  is  diffi- 
cult to  observe  that  flower-buds  had  been  formed. 

Like  the  apple,  the  fruit-buds  of  the  pear  are  not  likely 
to  be  injured,  but  the  spur  itself  may  be  killed  with  the  con- 
sequent destruction  of  the  fruit-bud. 

As  a  rule,  the  more  commonly  grown  varieties  of  the  sour 
cheriy  are  hardy  in  buds  as  far  north  as  central  New  Eng- 
land, except  in  veiy  extreme  win- 
ters or  when  low  temperatures 
follow  after  the  buds  have  swollen. 
On  the  other  hand,  Macoun  -  re- 
ports that  in  the  fruit-growing 
sections  of  Canada  the  cherry, 
like  the  European  and  Japanese 
plums,  is  injured  more  or  less 
eveiy  winter  when  not  protected 
1)}'  some  body  of  water.  Similar 
injuiy  to  the  buds  of  early  Rich- 
mond cherries  was  reported  in 
Wisconsin  after  the  winter  of 
1917-18.3     (Fig.  34). 

The  sweet  cherry  is  much  less 
reliable  than  the  sour  cherry;  in 
fact  it  is  not  much  more  hardy 
than  the  peach. 

Varieties  of  the  plum  vary  widely  in  their  hardiness. 
Many  of  the  American  species  (such  as  Prunus  nigra)  are 
very  hardy,  while  others  are  not.  Some  varieties  of  P. 
salicina,  such  as  the  Burbank,   also  are  reasonably  hardy 

1  ^\^lipple,  O.  B.     Mont.  Agr.  Exp.  Sta.  Bull.  91.     1912. 

2  Canada  Exp.  Farm,  Kept.  1907-08.    pp.  110-116. 
'  Proc.  Soc.  Hort.  Sci.    15th  Kept.  1918.    p.  32. 


Fig.  34. — Fruit-bud  of  sour 
cherry.  Left,  flower-bud 
alive;  right,  flower-bud 
killed. 


256 


POMOLOGY 


in  the  northern  latitudes.  The  European  plums,  while 
not  tender,  are  usually  not  so  hardy  as  other  species  and 
are  not  widely  grown  so  far  north  as  New  England  and 
Canada,  although  this  again  is 
somewhat  a  varietal  character- 
istic. 

The  buds  of  the  peach  are  the 
most  tender  of  any  of  the  tree- 
fruits  commonly  grown  in  the 
northern  United  States.     Varie- 

ties  vary  markedly  and  no  def- 

l^fe    S^^^^H^^^I      inite    point    of    injury    can    be 

•*  -■  ai^H^H^^H      stated,  but  a  temperature  from 

18°  to  20°  F.  below  zero  is  likely 

to  destroy  all  the  fruit-buds  and 

hence  the  crop. 

222.  Injury  to  the  woody  parts 
above  ground. — While  a  loss  of 
the  fruit-buds  is  a  serious  eco- 
nomic factor,  the  injury  that 
may  occur  to  the  tree  itself  is 
more  destructive  in  its  nature. 
Winter  injuiy  to  fruit-trees  may 
take  sevei-al  forms,  some  being 
rather  characteristic  of  one  sec- 
tion and  some  of  another  or  all 
forms  may  occur  in  a  given 
region.  The  following  are  the  more  important  types  of  such 
injury:  killing  of  the  terminal  growth  of  the  shoots;  killing 
of  patches  of  tissue  on  the  limbs  or  body  of  the  tree;  crotch 
injury;  "black  heart";  collar-rot;  frost-cracks;  frost-cankers; 
and  sun-scald. 

223.  The  killing  of  the  terminals  on  many  kinds  of  fruit- 
trees,  even  the  more  hardy  ones,  is  common  in  a  severe  win- 


FiG.  35. — Winter  injury  on 
trunk  of  a  Baldwin  apple 
■tree. 


WINTER  INJURY  257 

ter.  This  is  particularly  true  if  the  growth  has  continued 
late  and  has  not  matured  well  the  previous  season.^  It 
may  also  be  due  to  an  inherent  tenderness  of  the  varieties. 
The  result  of  this  injury  is  much  the  same  as  from  cutting 
or  shearing  back  the  terminal  growth;  that  is,  the  uninjured 
buds  nearest  the  terminal  will  make  a  longer  growth  than 
if  no  injuiy  had  occurred,  while  the  more  proximal  ones  are 
likely  to  remain  dormant. 

224.  Killing  of  patches  or  areas  of  bark  on  the  Umbs  and 
trunk  is  also  a  common  type  of  injury.  This  will  first  ap- 
pear as  a  sunken  area  which  eventually  dries  and  cracks. 
It  is  thought  that  considerable  of  the  black-rot  canker 
(Sphccropsis  malorum,  Peck)  so  common  on  the  apple  in 
some  sections  is  due  to  the  entrance  of  disease  spores  through 
openings  in  the  bark  caused  by  the  splitting  or  drying  out 
of  the  dead  areas.  This  type  of  injuiy  may  also  take  the 
form  of  frost-cankers.     (Fig.  35). 

Large  dead  areas  on  the  trunks  of  the  older  trees  are  also 
conunon  in  the  more  northern  sections,  particularly  on  Bald- 
win and  King  apple  trees.  This  injury  is  occasioned  by  much 
the  same  set  of  conditions  as  produced  the  dead  areas  on 
the  smaller  branches.  It  is  somewhat  more  serious,  how- 
ever, for  there  is  opportunity  to  remove  an  injured  branch 
but  it  is  difficult  to  repair  damage  to  the  trunk.  The  bark 
in  this  case  will  loosen  and  come  off.  Unlike  sun-scald  this 
injuiy  does  not  occur  on  any  particular  side  of  the  tree. 

225.  Crotch  injury  is  characterized  by  a  kilHng  of  the 
tissues  in  the  forks  or  crotches  of  both  large  and  small 
branches.  The  injury  may  be  restricted  to  a  small  area  or  it 
may  be  more  extensive.  Many  varieties  of  apple  may  be  af- 
fected, such  as  Ben  Davis,  Baldwin,  Rhode  Island  Green- 
ing, and  even  Northern  Spy.     Several  theories  have  been 

^  Emerson,  R.  A.  The  relation  of  early  maturity  to  hardiness  in 
trees.    Nebr.  Agr.  Exp.  Sta.    19th  Ann.  Rept.     1906.    p.  101-110. 


258  POMOLOGY 

propos9d  to  account  for  crotch  injury,  such  as  drying  out, 
occurrences  of  ice  at  these  points,  and  immaturity  of  the 
wood.  The  latter,  according  to  Chandler,^  is  the  principal 
if  not  the  only  factor  involved.  The  last  tissue  formed  and 
hence  the  most  tender  is  near  the  base  of  the  branches 
(crotches)  and  near  the  bottom  of  the  trunk  of  the  tree. 
This  tissue  becomes  more  hardy  or  mature  as  the  season 
advances.  Hence,  if  veiy  low  temperatures  occur  early  in 
the  winter,  this  tissue  is  the  first  that  is  injured.  If  the  pre- 
vious growing  season  is  short  and  the  tree  as  a  whole  goes  into 
winter  in  an  innnature  condition,  the  damage  is  enhanced. 

226.  Collar-rot  or  injury  is  an  affection  of  fruit-trees 
localized  at  the  crown  or  "collar."  The  injury  may  extend 
down  on  to  the  larger  roots  and  also  some  distance  up  the 
trunk  and  it  frequently  encircles  the  base  of  the  tree,  result- 
ing in  its  death.  Such  varieties  of  apple  as  the  Grimes,  Grav- 
enstein,  and  King  are  particularly  susceptible  and  for  this 
reason  they  are  often  top-worked  on  to  resistant  sorts.  The 
cause  has  been  variously  attributed  to  arsenical  poison- 
ing,2  parasitic  organisms,  and  to  freezing. 

Grossenbacher  has  shown  that  the  primaiy  injury  takes 
place  in  the  winter  in  connection  with  severe  freezing 
weather  and  hence  that  fungi  are  not  the  chief  cause  but  are 
the  agencies  of  decay  following  the  winter  injury.  Chandler 
has  also  pointed  out  that  blight  {Bacillus  amylovorus)  is  not 
the  cause  of  collar-rot  since  the  result  of  "body  bUght"  is 
a  tightening  of  the  bark  when  it  dies,  which  is  the  opposite 
phenomenon  of  true  collar-rot.  The  latter  also  holds  that 
collar-rot  is  doubtless  due  to  direct  freezing  to  death  from 
the  low  temperature  and  frequently  to  a  rapid  lowering  of 

1  Chandler,  W.  H.    Mo.  Agr.  Exp.  Sta.  Res.  Bull.  8.    1913. 

2  Headden,  W.  P.  Colo.  Agr.  Exp.  Sta.  Bull.  131.  1908.  Grossen- 
bacher, J.  G.  N.  Y.  (Geneva)  Exp.  Sta.  Tech.  Bull.  12  and  23.  1909 
and  1912. 


WINTER  INJURY  259 

the  temperature,  and  not  to  a  tearing  of  the  tissue  or  drying 
out  as  described  by  Grossenbacher. 

That  excessive  alkali  soils  and  arsenical  poisoning  are  pri- 
mary factors  in  collar-rot  has  also  been  generally  abandoned 
through  the  work  of  Headden  ^  and  Ball "  in  the  first  case  and 
Ball  ^  and  his  associates  in  the  second. 

The  view  was  held  by  Headden  that  large  quantities  of 
arsenic  were  found  in  trees  suffering  from  collar-rot,  but  the 
fact  that  normal  trees  also  often  contained  fairly  large  quan- 
tities of  arsenic,  that  collar-rot  occurred  in  orchards  which 
had  never  been  sprayed,  and  that  herbaceous  plants  were 
growing  about  crown-rotted  trees,  caused  this  view  to  be 
abandoned  for  the  one  of  freezing. 

227.  Frost-cracks  or  the  splitting  of  bark  or  trunks  of 
trees  often  accompanies  other  forms  of  winter  injuiy. 
These  cracks  may  extend  up  the  entire  length  of  the  trunk 
and  follow  up  one  or  more  of  the  main  branches  for  some 
distance,  or  they  may  be  only  a  few  inches  in  length.  They 
may  open  as  much  as  two  centimeters  or  may  be  merely 
visible  lines,  but  in  any  event  they  will  draw  together  or 
clos(»  after  the  severe  weather  is  over. 

228.  "  Black  heart "  is  a  common  result  of  low  tempera- 
tures and  consists  in  the  killing  of  the  sap-wood  and  pith, 
although  the  cambium  remains  alive.  As  a  result,  the  tree 
continues  growth  and  rapidly  forms  a  new  layer  of  sap-wood 
within  and  bark  without.  Nursery  trees  are  frequently 
"black  hearted,"  particularly  pears,  and  they  may  make  a 

Note  :— Following  the  winter  of  1917-18  the  author  inspected  several 
orchards  of  Ben  Davis  trees  in  the  state  of  Maine  in  which  the  damage 
took  the  form  of  crotch  injury  almost  entirely  and  while  the  trees  were 
partly  alive  they  were  entirely  beyond  hope  of  repair. 

1  Headden,  W.  P.    Colo.  Agr.  Exp.  Sta.  Bull.  157.    1910. 

2Ball,  E.  D.    Jour.  Econ.  Ent.  2:  142-48.    1909. 

3  Ball,  E.  D.  el  al.    Jour.  Econ.  Ent.  3:  187-97.    1910. 


260  POMOLOGY 

stunted  growth  or  soon  recover,  depending  on  the  extent 
of  the  injury  and  on  the  growing  conditions  immediately 
following  planting.  Mature  trees  in  some  sections  are  often 
"black  hearted"  throughout  their  lives  with  no  apparent 
incapacity. 

229.  Sun-scald  is  manifest  by  a  dead  area  on  the  south- 
west (sun-exposed)  side  of  the  trunk  of  the  tree.  This  dam- 
age, unlike  the  other  forms  discussed  above,  occurs  late  in 
the  winter  when  days  of  bright  sunshine  follow  cold  nights. 
The  cause  has  usually  been  assigned  to  a  starting  of  growth 
or  sap  movement  on  the  side  of  the  tree  exposed  to  the  sun 
which  activity  is  inmiediately  followed  by  severe  freezing. 
However,  Chandler  does  not  credit  this  view  from  his  work 
with  winter  injury  but  suggests  that  the  tissue  is  warmed 
by  the  sun  until  the  temperature  nearly  reaches  the  freezing 
point  when  a  sudden  drop  will  cause  the  tissue  to  ''freeze 
to  death."  ^ 

230.  Root-killing. — -This  form  of  injury  is  likely  to  be 
general  during  a  severe  winter  when  the  ground  is  bare.  It 
is  well  known  that  bare  ground  will  freeze  much  deeper  than 
when  the  surface  is  protected  by  some  sort  of  cover,  but 
no  cover  of  vegetation  is  equivalent  to  a  deep  snowfall  which 
lies  on  the  ground  throughout  the  winter."  Such  hardy  va- 
rieties as  Mcintosh  and  Wealthy  will  be  root-killed  as  readily 
as  the  more  tender  sorts,  like  Baldwin  and  Wagener,  in  a 
snowless  winter,  although  the  trunks  and  branches  of  the 
latter  varieties  would  show  severe  injury  while  none  might 
appear  on  the  hardy  sorts. 

Chandler  has  shown  that  the  roots  are  the  tenderest  part 
of  the  tree,  and  that  the  portions  nearest  the  crown  are  the 
most  resistant,  while  the  smaller  remote  rootlets  are  the  most 

'  See  also  Mix,  A.  J.    Sun-scald  of  fruit-trees  a  type  of  winter  injury. 
Cornell  Univ.  Agr.  Exp.  Sta.  Bull.  382.     1910. 
2  Neb.  Agr.  Exp.  Sta.  Bull.  79,  92.    1903,  1906. 


WINTER  INJURY  261 

tender.  From  his  experiments  he  concludes  that  apple  roots 
will  be  killed  at  about  —3°  C.  in  summer  when  they  are  ten- 
derest  and  at  about -12°  C.  in  late  winter  with  rapid  freez- 
ing, this  varying  somewhat  with  conditions.  He  also  shows 
that  French  crab  stock  is  less  hardy  in  the  roots  than  the 
cion-roots  of  such  varieties  as  Ben  Davis;  that  "Marianna 
plum  roots  are  more  hardy  than  Myrobolan  roots,  and  IVIah- 
aleb  cheriy  roots  seem  slightly  more  hardly  than  Mazzard 
roots." 

231.  How  freezing  kills. — A  distinction  is  made  between 
the  loss  of  fruit  crops  by  ''killing  frosts"  and  by  "freezing." 
The  latter  is  here  considered  in  studying  the  destruction  of 
the  tissues  of  fruit-trees.  It  is  generally  accepted  that 
the  freezing  to  death  of  plant  tissues  does  not  take  place 
unless  ice  crystals  are  formed  within  the  plant  from  water 
that  has  been  withdrawn  from  the  cells.  While  ice  crystals 
may  form  within  the  cells  themselves  when  the  temperature 
falls  veiy  rapidly,  the  above  method  is  much  the  more  com- 
mon. It  was  formerly  considered  that  much  less  injury 
w'ould  result  if  thawing  of  the  tissue  was  gradual  so  that  the 
cells  could  again  take  up  the  moisture,  assuming,  of  course, 
that  the  cells  had  not  been  ruptured  in  the  process  of  freez- 
ing. Later  investigators  ^  have,  however,  shown  that  the 
rate  of  thawing  has  nothing  to  do  with  the  killing  of  the  tis- 
sue, except  with  ripe  apples  and  pears,  lettuce,  and  the 
leaves  of  Agave  americana,  but  that  the  killing  occurs  when 
a  sufficiently  low  temperature  is  reached. 

"Frozen  to  death"  is  a  technical  phrase  describing  plant 
tissues  that  have  been  subjected  to  a  certain  temperature 
at  which  death  of  their  cells  occurs.  Such  tissues  present  a 
brown,  water-soaked  appearance  shortly  after  they  thaw 
and  evaporation  is  much  more  rapid  than  from  living  tissue. 

'  Miiller-Thurgau,  Chandler,  et  al  Mo.  Agr.  Exp.  Sta.  Res.  Bull-  S. 
p.  150. 


262  POMOLOGY 

232.  Hardiness  of  different  tissues. — As  has  been  in- 
dicated above,  the  different  tissues  of  a  fruit-tree  vary  in 
hardiness,  and  they  also  change  at  different  seasons  of  the 
year.  It  has  been  shown  that  when  the  trees  are  in  a  young 
growing  condition,  the  cambium,  young  cortex,  and  sap-wood 
cells  are  the  tenderest  while  the  pith  in  young  twigs  is  the 
first  to  be  killed  in  mature  trees  followed  by  browning  in  the 
sap-wood  and  the  outer  or  old  cells  of  the  cortex.  The  nota- 
ble point  here  is  that  cambium  is  most  tender  in  the  grow- 
ing plant  but  relatively  hardy  when  it  is  in  winter  condition. 
This  observation  can  sometimes  be  made  with  peach  trees 
after  a  severe  winter  when  a  cross-section  of  the  limbs  or 
trunk  will  often  look  so  brown  or  black  that  little  or  no  hope 
could  be  entertained  for  saving  them.  The  cambium  may 
start  into  growth  in  the  spring,  however,  and  soon  a  new  layer 
of  sap-wood  is  formed,  which  begins  functioning,  and  re- 
covery of  the  tree  takes  place. 

The  fruit-buds  of  the  peach  are  recorded  to  be  about  as 
hardy  as  the  cortex,  cambium,  and  sap-wood  of  the  twigs  in 
the  latter  part  of  summer,  but  during  the  winter  they  are 
the  most  tender  of  all  the  tissues  above  ground  with  the  pos- 
sible exception  of  the  pith  cells.  Usually  the  leaf-buds  are 
more  hardy  than  the  fruit-buds,  but  instances  are  on  rec- 
ord in  which  the  leaf-buds  and  part  of  the  sap-wood  of  the 
peach  have  been  killed  or  badly  injured  while  a  portion  of 
the  fruit-buds  have  survived  and  produced,  even  in  the  ab- 
sence of  leaves.^  This  is  explained  on  the  basis  of  lack  of 
maturity  of  the  wood  tissue,  while  the  fruit-buds  reached 
maturity  before  the  freezing  occurred. 

233.  Rest-period. — That  perhaps  all  plants  have  a  more 
or  less  definite  rest-period  has  been  well  established  by  a 
number  of  writers,  notably  Klebs  in  Germany  and  Whit- 

1  Chandler,  W.  H.  hoc.  cit.  p.  224.  Paddock,  W.  Soc.  Hort.  Sci. 
1918.    p.  30. 


WINTER  INJURY  263 

ten  ^  and  Howard  -  in  this  country.  This  phenomenon  can  be 
observed  with  different  varieties  of  the  same  kind  of  fruit  by 
the  early  swelling  of  buds  and  time  of  starting  into  growth. 
For  the  more  southern  peach-growing  sections  that  are  in 
the  danger  belt  for  spring  frosts,  the  length  of  the  rest-period 
becomes  of  serious  importance,  for  the  more  forward  vari- 
eties are  most  likely  to  be  lost  from  freezes  and  frosts.  In 
order  to  shift  the  resting-period  to  later  in  the  winter,  a 
series  of  experiments  were  conducted  by  Whitten  to  cause 
the  trees  to  enter  their  rest-period  at  a  later  time  and  hence 
make  them  correspondingly  later  in  awakening  from  this 
state.  By  means  of  late  cultivation,  it  was  possible  to  delay 
the  rest-period  and  as  a  result  the  trees  were  a  few  days  later 
in  blossoming  than  was  the  case  under  normal  conditions. 

FACTORS  INVOLVED  IN  FREEZING 

234.  Maturity. — Reference  has  already  been  made  to 
the  importance  of  having  the  tissues  well  matured  if  injury 
from  low  temperatures  is  to  be  avoided.  It  has  been  estab- 
lished experimentally  ^  as  well  as  by  extensive  observation 
that  maturity  is  the  most  important  single  factor  involved. 
While  the  nature  of  the  season  is  beyond  the  control  of  man, 
certain  horticultural  practices  should  be  followed  in  order 
to  bring  about  as  great  a  degree  of  maturity  as  possible. 
These  will  be  considered  later. 

It  has  been  observed  that  the  hardiest  varieties  mature 
early  in  the  season.  Macoun  has  studied  the  effect  of  winter 
on  a  large  number  of  plants  at  Ottawa,  Canada,  for  a  period 
of  twenty-two  years,  having  under  his  obsei-vation  over 
3000  species  and  varieties,  many  of  which  kill  back  more  or 

1  Whitten,  J.  C.    Mo.  Agr.  Exp.  Sta.  Bull.  38.    1897. 

2  Howard,  W.  L.    Mo.  Agr.  Exp.  Sta.  Res.  Bull.  1.    1910. 

'  Neb.  Agr.  Exp.  Sta.  Bull.  79  and  92.  1903,  1906.  Ohio  Agr.  Exp. 
Sta.  Bull.  192.    1908.    N.  Y.  (Geneva)  Agr.  Exp.  Sta.  Bull.  269.    1905. 


264  POMOLOGY 

less  every  year.  All  those  which  kill  back  more  or  less  regu- 
larly are  native  to  regions  having  a  longer  growing  season 
than  that  at  Ottawa  and  hence  they  mature  too  late  there 
and  the  wood  is  not  thoroughly  ripened.  He,  therefore,  con- 
cludes that  a  tree  or  shrub  which  will  withstand  a  test  win- 
ter at  Ottawa  must  ripen  its  wood  early.  ^  Not  only  do  the 
more  mature  trees  exhibit  greater  hardiness,  but  they  also 
become  more  hardy  as  the  winter  advances  until  they  again 
respond  to  growing  conditions  as  spring  approaches.  While 
writers  have  connnonly  assigned  the  reason  for  lack  of  hardi- 
ness to  a  higher  moisture-content  of  the  tissue,  Chandler 
has  shown  that,  with  the  exception  of  the  cambium,  the  tis- 
sue contains  as  much  moisture  later  in  the  winter  when  it  is 
more  hardy  as  when  it  enters  the  dormant  period.  "It 
would  seem  highly  probable  that,  except  in  the  case  of  cam- 
bium, the  additional  hardiness  acquired  by  the  different 
tissues  of  the  tree  as  they  pass  into  Avinter,  is  due  to  a  change 
in  the  protoplasm  such  that  it  can  withstand  the  great  loss 
of  water  rather  than  a  change  in  the  percentage  of  moisture 
or  in  sap  concentration.  It  is  also  possible  that  changes  in 
the  sap  solute  that  lower  its  eutectic  point  may  occur  and 
that  these  may  increase  the  resistance  to  cold  by  holding 
water  unfrozen  to  protect  the  protoplasm  from  too  com- 
plete desiccation  at  lower  temperatures." 

An  additional  point  of  evidence  that  maturity  and  growth 
conditions  the  previous  season  affect  the  resistance  of  trees 
to  cold,  is  the  observation  that  trees  having  their  foliage 
injured  or  destroyed  by  insects  or  spray  burning  suffer  seri- 
ous killing  of  the  wood.  Also  the  inner  surface  of  branches 
which  possess  less  foliage  is  nearly  always  more  tender  than 
the  exposed  sides.  ^ 

1  Proc.  Amer.  Soc.  Hort.  Sci.     1912.    p.  59. 

2  Proc.  Amer.  Soc.  Hort.  Soc.  15th  Rept.  1918.  p.  18.  Card,  F.  W. 
Bush-Fruits.    Macmillan  Co.,  Rev.  Ed.,  1917.     p.  56. 


WINTER  INJURY  265 

235.  Sap  concentration. — The  work  of  Chandler  on  the 
relation  of  sap  concentration  to  the  freezing  of  plant  tissue  is 
particularly  important.  The  experiments  of  Miiller-Thur- 
gau  and  Molisch  had  previously  shown  conclusively  that 
practically  all  the  formation  of  ice  ciystals  takes  place  in 
the  intercellular  spaces  and  only  rarely  (due  to  very  rapid 
freezing)  in  the  cells  themselves.  Furthermore,  if  the  proto- 
plasm or  membrane  surrounding  it  fails  to  give  up  its  Avater, 
the  freezing  point  is  thereby  lowered  or,  in  other  words,  a 
protection  is  afforded.  They  also  observed  that  tissue  could 
be  super-cooled,  just  as  a  liquid,  to  a  lower  temperature  than 
that  at  which  ice  would  normally  form  in  the  intercellular 
spaces,  and  be  raised  again  without  ice  formation  and  hence 
without  injuiy. 

Chandler  has  shown  that  if  the  sap  concentration  could  be 
doubled  it  would  inhibit  the  loss  of  water,  for  twice  as  much 
would  l)e  held  in  the  protoplasm  "at  any  given  temperature 
below  the  freezing  point,  but  above  the  eutectic  point  ^  of 
the  solute,"  as  a  protection  against  freezing.  Extensive 
experiments  were  conducted  with  various  kinds  of  herba- 
ceous and  woody  plants  and  their  fruits  and  leaves  to  de- 
termine whether  lowering  their  sap  concentration  would 
lower  their  freezing  point.  The  sap  concentration  was  low- 
ered by  placing  the  plants  in  or  by  watering  with  solutions 
of  various  salts,  sugars,  or  glycerine.  The  freezing  point  of 
the  sap  was  then  determined  and  reported  in  the  terms  of 
"depression,"  which  means  "the  number  of  degrees  centi- 
grade below  zero  at  which,  with  no  supercooling,  ice  forma- 
tion begins  in  the  sap." 

The  following  table  (after  Chandler)  illustrates  how  uni- 

i"By  the  eutectic  point  is  meant  the  temperature  at  which  the 
substance  in  soUition  crystallizes  out.  At  that  temperature  there 
would  be  at  the  same  time  ice,  crystals  of  solute,  and  unfrozen 
solutions," 


266 


POMOLOGY 


versally  the  lowering  of  the  sap  concentration  (from  any 
cause)  has  lowered  the  freezing  point: 


Table  LXXIX 

relation  of  sap  concentration  to  freezing 

young  fruits 


Depression 


Cherries  fresh  from  tree 

Cherries  from  twigs  with  ends  in  glycerine  sixteen  hours. . 

Cherries  wilted  five  hours 

Peaches  fresh  from  tree 

Peaches  from  twigs  with  ends  in  glycerine  sixteen  hours .  . 

Peaches  wilted  five  hours 

Apples  from  twigs  with  ends  in  glycerine  thirty  hours.  .  .  . 

Apples  from  twigs  with  ends  in  water  thirty  hours 

Apples  from  twigs  with  ends  in  cane  sugar  thirty  hours. .  . 
Apples  from  twigs  with  ends  in  glycerine  forty-eight  hourt- 


0.905 
1.180 
1,075 
0.965 
1.230 
1.085 
1.408 
1.335 
1.530 
1.417 


Thus  it  will  be  seen  from  these  data  that  wherever  the 
sap  concentration  of  young  fruits  has  been  lessened,  the 
temperature  at  which  it  will  freeze  has  been  reduced  also. 
The  same  results  were  secured  with  the  leaves  and  tender 
shoots  of  trees  and  with  more  succulent  plants  such  as  corn 
and  tomato.  Furthermore,  it  was  shown  that  the  sap  con- 
centration of  shaded  plants  is  lower  (i.  e.,  not  so  dense) 
than  that  of  unshaded  ones  and  hence  they  kill  at  a  higher 
temperature.  However,  all  of  these  researches  were  con- 
ducted with  succulent  plants,  and  not  with  woody  tissue 
in  the  dormant  or  resting-period. 


WINTER  INJURY 


267 


Table  LXXX 

data  showing  influence  of  shading  on  the  killing  of  tissue 

(aftek  chandler) 


Material 

Treatment 

Date 

Temper- 
°C.i 

Number 

of 
plants 

Percent- 
age all 
killed 

Percentage 

total 

leaf  area 

killed 

Depres- 
sion 

Early  Harvest 
apple  twig 
and  leaves 

Shaded 

June  28 

— i 

39 

0.0 

3o.9 

1.975 

do. 

Not  shaded 

June  28 

— i 

42 

0.0 

0.8 

2.438 

do. 

Shaded 

June  28 

—5 

47 

34.0 

70.0 

1.975 

do. 

Not  shaded 

June  28 

—5 

50 

0.0 

48.5 

2.438 

In  order  to  deternihie  whether  such  tissue  could  also  be 
influenced  in  like  mamier  by  appljnng  fertilizers,  a  heavy 
application  of  potassium  chlorid  (500  pounds  to  the  acre) 
was  made  to  peach  orchards  in  different  locations  over  a 
period  of  four  years.  No  difference  appeared,  however,  in 
the  amount  of  winter-killing  of  the  wood,  hardiness  of  the 
fruit-buds,  or  of  the  bloom  when  spring  frosts  occurred. 
However,  on  determining  the  sap  concentration  of  twigs  from 
these  treated  trees,  no  difference  appeared;  hence,  accord- 
ing to  the  previous  observations  with  other  plants,  no  differ- 
ence in  hardiness  could  be  expected.  The  suggestion  is  made 
that  if  it  were  possible  to  increase  the  sap  concentration 
by  the  use  of  fertihzers,  some  difference  in  hardiness  of  the 
blooms  would  be  anticipated. 

236.  Rate  of  freezing  a  factor. — Very  conclusive  data 
are  available  to  establish  that  a  rapid  fall  in  temperature  is 
much  more  injurious  than  a  gradual  one,  either  with  tissue 
after  the  sap  is  flowing  or  when  it  is  entirely  donnant;  par- 
ticularly is  this  true  with  the  buds.      It  has  also  been  shown 

^  To  convert  centigrade  and  Fahrenheit  temperatures: 

F.  —  32 
Degrees  — — - —  =  Degrees  C. 
1 .8 

Degrees  C.  X  1.8  +  32  =  Degrees  F. 


268 


POMOLOGY 


that  a  rapid  fall  of  temperature  near  the  freezing  point  is 
more  harmful  than  near  the  point  at  which  the  tissue  is 
killed  and  this  fact  is  applied  as  a  possible  explanation  of 
"sun-scald"  of  apple  trees. 

The  following  excerpts  from  Chandler's  data  illustrate 
this: 

Table  LXXXI 

the  effect  of  slow  and  rapid  lowering  of  temperature  on  the 
killing  of  plant  tissue 


Kind  of  buds 


Date 


Niwibcr 
buds 


Percent, 
killed 


Number 
buds 


Percent, 
killed 


Slowly  to 
—18°  C. 


Rapidly  to 
—13.5°  C. 


Rice's  seedling  peach 

Elberta  peach 

Jonathan  apple 

Montmorency  cherry 
Chabot  plum 


Mar.  22 
Mar.  22 
Mar.  22 
Mar.  22 
Mar.  22 


138 
100 
34 
176 
236 


44.2 
88.0 
64.7 
58.5 
78.3 


154 
85 
33 
184 
183 


51.9 
92.9 
75.7 
62.5 
86.8 


When  twigs  of  the  apple,  peach,  cherry,  and  plum  were 
exposed  to  a  temperature  which  gradually  fell  to  — 18°  C, 
the  killing  was  about  the  same  as  when  it  fell  rapidly  to 
—  13.5°  C.  These  with  other  data  show  conclusively  that 
both  buds  and  wood  are  more  surely  injured  if  the  tempera- 
ture drops  rapidly  than  slowly,  even  though  it  does  not  go 
so  low  in  the  rapidly  frozen  tissues. 

237.  Protection  of  bud  scales. — It  has  usually  been 
assumed  that  the  bud  scales  afford  protection  from  cold  as 
well  as  prevent  loss  of  moisture  from  or  entrance  of  water 
into  the  buds.  However,  this  has  not  held  true  experi- 
mentally ^  for  buds  which  had  their  scales  removed  were 
not  frozen  any  quicker  or  at  a  higher  temperature  than  were 
1  Wiegand,  K.  M.     Bot.  Gaz.,  Vol.  41,  pp.  373-424. 


WINTER  INJURY  269 

such  buds  with  their  scales.  This  work  was  done  with 
peaches  only,  and  they  were  treated  on  different  dates  from 
February  26  to  March  12.  The  temperature  was  reduced 
to  various  points  from  —  10°  C.  to  —22.5°  C.  with  the  follow- 
ing average  results: 

Total  number  of  buds,  scales  off,  4430,  51.0  per  cent 
killed;  total  number  of  buds,  scales  on,  5078,  68.5  per  cent 
killed. 

238.  Relation  of  crop  the  preceding  season. — It  has  been 
observed  in  various  sections  of  the  country  that  trees  which 
fruit  heaviest  are  most  likely  to  be  injured  by  very  low 
temperatures  the  winter  immediately  following.  This  ob- 
servation was  repeatedly  reported  after  the  severe  winter 
of  1917-18. 

Macoun  describes  a  row  of  Wealthy  apple  trees  (21  years 
old)  at  Ottawa  that  behaved  in  this  way.  Of  fourteen  trees, 
the  eight  which  bore  a  medium  to  heavy  crop  in  1917  were 
killed  or  badly  injured,  while  the  six  bearing  either  a  light 
crop  or  none  at  all  came  through  the  winter  in  good  condi- 
tion.^ 

In  New  York  state  and  in  New  England  it  was  noted  that 
hardy  varieties  of  the  apple  were  killed  more  readily  than 
such  tender  sorts  as  the  Baldwin,  if  the  former  had  set  a 
heavy  crop  the  preceding  season  while  the  latter  had 
not. 

This  result  was  earlier  indicated  when  it  was  shown  that 
well  thinned  peach  trees  seemed  to  be  more  resistant  than 
unthinned  ones  which  bore  a  heavy  crop:  ^  average  per- 
centage of  peach  buds  killed,  tree  thinned,  35.4;  average 
percentage  of  peach  buds  killed,  trees  not  thinned,  51.4. 

239.  Correlation  of  wood  structure  and  hardiness. — 
Various  attempts  have  been  made  to  discover  any  correla- 

1  Proc.  Amer.  Soc.  Hort.  Sci.    1918.    p.  17. 
^  Mo.  Agr.  Exp.  Sta.  Bull.  74.    1907. 


270  POMOLOGY 

tion  that  might  exist  between  the  wood  structure  or  other 
morphological  characters  and  the  hardiness  of  plants.  Hal- 
sted  ^  made  a  special  investigation  and  reported  that  "No 
constant  difference  in  all  structures  probably  exists  among 
apple  twigs  by  means  of  which  one  sort  may  be  umnistak- 
ably  distinguished  from  all  others.  Much  less  is  there  any 
point  in  minute  structure  invariably  present  with  those  sorts 
which  are  classed  as  hardy  and  absent  from  tender  vari- 
eties. Maturity  of  twigs  is  a  condition  of  successful  win- 
tering, and  therefore  the  so-called  hardy  sorts  are  quite  sure 
to  finish  their  seasons'  growth  before  autumn  frosts  arrive." 

More  recently  Beach  and  Allen  ^  conducted  some  exten- 
sive investigations  on  this  problem,  and  observed  a  large 
number  of  plant  characters  of  hardy  and  tender  varieties  of 
fruits.  In  general,  no  outstanding  and  consistent  correla- 
tions could  be  found,  but  they  report  that  "The  hardier 
varieties  on  the  average  had  a  slightly  lower  moisture  con- 
tent than  the  more  tender  varieties,"  also  "Large,  thick 
petals  are  correlated  with  hardiness,  although  the  converse 
of  this  is  not  always  true." 

240.  Influence  of  type  of  soil. — Inasmuch  as  the  type  of 
soil  materially  influences  the  maturity  of  the  trees,  this 
factor  becomes  one  of  importance  in  studying  winter  injury. 
In  general,  a  soil  that  is  heavy  and  inclined  to  be  wet  will 
delay  maturity  and  hence,  other  things  being  equal,  there 
would  usually  be  more  winter  injury  on  such  a  soil  than  on 
one  of  a  lighter  nature.  This  is  particularly  true  of  the  sub- 
soil, as  indicated  in  Chapter  VII.  Bouyoucos  ^  has  shown 
that  a  heavy  soil  contains  more  moisture  and  will  not  freeze 
so  deeply  as  a  lighter  one,  although  a  sand  or  gravel  will 

1  Halsted,  B.  D.  Iowa  Agr.  Exp.  Sta.  Bull.  4.  1889.  Mem.  Torrey 
Bot.  Club,  2:  1,  26. 

2  Iowa  Agr.  Exp.  Sta.  Res.  Bull.  21.    1915. 

3  Bouyoucos,  G.  J.    Mich.  Agr.  Exp.  Sta.  Tech.  Bull.  26,     1916. 


WINTER  INJURY  271 

fluctuate  more  with  the  air  temperature  than  the  heavy  soil 
because  of  the  difference  in  specific  heat.^ 

Hedrick  -  reports  on  the  experience  of  Michigan  and  New 
York  growers  with  the  peach.  In  the  first  case  the  growers,  al- 
most without  exception,  considered  a  sandy,  gravelly,  or  stony 
soil  much  more  favorable  to  peach-growing  and  that  peach 
trees  are  more  hardy  in  such  a  soil  than  in  a  heavy  one. 

Bouyoucos  investigated  the  depth  and  rate  of  freezing 
of  the  following  types  of  soil:  gravel,  sand,  loam,  clay,  and 
peat.  It  was  found  that  "they  all  froze  about  the  same 
time  in  the  upper  6  inches,  but  in  the  spring  they  thawed  and 
warmed  up  at  different  rates.  This  was  attributed  to  their 
different  specific  heats  and  to  the  downward  and  upward  trend 
of  air  temperature  in  the  fall  and  spring  respectively.  The 
gravel  and  sand  thawed  first,  followed  by  clay  1  day  later, 
loam  2  days  later,  and  peat  10  days  later.  After  they  were 
entirely  thawed  out  all  the  types  of  soil  had  almost  the  same 
temperature  from  then  on  throughout  the  summer,  autumn, 
and  winter." 

He  further  shows,  however,  that  if  very  cold  weather  is 
experienced  early  in  the  winter  without  any  fluctuations  in 
temperature,  the  light  soil  freezes  deeper  than  the  heavy 
ones,  thus  giving  an  advantage  to  higher  moisture-content 
in  such  a  case.  In  New  York  state,  however,  the  growers 
would  not  distinguish  between  a  heavy  and  a  light  soil  so 
far  as  winter  injur}'-  is  concerned,  provided  the  heavy  soil 
is  "warm  and  dr}^"  In  both  states  the  growers  preferred 
a  gravelly  subsoil  in  order  to  secure  a  hardy  tree. 

^  There  would  seem  to  be  a  discrepancy  between  this  statement 
and  the  one  following  by  Heth-ick,  but  this  is  probably  explained  by 
the  fact  that  trees  growing  on  clay  soil  usually  mature  later  and  hence 
are  more  subject  to  injury  in  the  tops.  If  the  injurj^  occurred  in  the  roots 
rather  than  in  the  tops,  it  would  be  much  worse  in  the  sandy  soil. 

2  Hedrick,  U.  P.    Trans.  Mass.  Hort.  See.  1919. 


272  POMOLOGY 

As  to  the  moisture  of  the  soil,  Hedrick  reports  that 
"Either  extreme  of  moisture — excessive  wetness  or  excessive 
dryness — gives  favorable  conditions  for  winter-killing.  A 
wet  soil  is  conducive  to  sappiness  in  the  tree  and  also  freezes 
deeply."  It  was  also  reported  that  a  very  dry  soil  failed  to 
furnish  the  trees  with  sufficient  moisture  during  winter  and 
the  buds  and  twigs  died  out  and  serious  winter-killing 
followed.^ 

241.  Proximity  to  bodies  of  water. — The  proximity  of 
an  orchard  to  a  large  body  of  water  has  a  greater  effect  on 
the  frost  injury  in  the  spring  than  on  winter  injury.  How- 
ever, an  effect  on  the  latter  is  not  infrequently  noted.  A 
conspicuous  example  of  this  is  seen  in  the  fruit  sections  bor- 
dering on  the  various  lakes.  "The  distance  to  which  the 
influence  of  a  body  of  water  will  extend  inland  depends  upon 
the  volume  of  water,  its  temperature  relative  to  that  of 
the  land,  the  area  of  its  free  surface,  the  slope  of  its  shores, 
and  the  prevailing  winds.  The  influence  of  Lake  Michigan, 
mainly  because  of  the  gentle  slope  of  its  eastern  shore,  ex- 
tends nearly  halfway  across  the  state  of  Michigan,  while 
the  influence  of  Lake  Erie,  because  of  the  abrupt  rise  of  its 
eastern  shore,  extends  inland  only  a  few  miles."  " 

Many  examples  could  be  noted  of  peach  orchards  favor- 
ably located  near  lakes  that  are  injured  only  in  the  most 
severe  winters,  while  sections  within  a  few  miles  frequently 
suffer  a  loss  of  the  crop  in  whole  or  in  part.  However,  the 
vagaries  of  winter  injury  seem  endless,  and  many  instances 
might  also  be  cited  where  such  an  influence  has  not  been 
noted. ^ 

1  See  also  Paddock,  W.    Colo.  Agr.  Exp.  Sta.  Bull.  142.    1909.    p.  11. 

2  Standard  Cyclo.  Hort.,  Bailey.    Vol.  3,  p.  1284.     (W.  M.  Wilson.) 
^  For  several  years  the  author  noticed  the  difference  in  date  of  bloom- 
ing of  apple  trees  near  the  Atlantic  coast  line  of  New  Hampshire  and 
inland,  showing  a  decided  retarding  effect  of  the  cold  winds  of  spring 


WINTER  INJURY  273 

242.  Topography  of  land. — While  it  would  seem  patent 
to  all  careful  observers  that  low  lands  suffer  much  oftener 
from  frosts  and  freezes  than  the  higher  elevations,  yet  many 
orchards  are  located  unfavorably  in  this  regard.  While 
the  average  temperature  of  the  air  decreases  at  the  rate  of 
1°  F.  for  each  300  feet  of  elevation  above  sea  level,  yet  it 
does  not  follow  that  more  injuiy  from  low  temperatures 
occurs  at  the  higher  elevations.  The  disturbing  factor  of 
wind  and  the  fact  that  cold  air  will  settle  and  flow  down  hill 
accounts  for  the  apparent  contradiction.  Here  again,  or- 
chards located  on  high  elevations  are  sometimes  injured  more 
than  those  at  lower  levels  during  severe  winters;  however,  the 
reverse  of  this  is  true  on  the  average.  Frost  pockets,  coves, 
and  flat  low  lying  lands  are  to  be  avoided  for  orcharding. 

In  some  of  the  western  fruit  sections,  the  reverse  of  this 
principle  holds  true,  owing  to  special  conditions.  In  some 
of  the  narrow  river  canyons,  the  fruit-trees  suffer  less  from 
injury  in  the  winter  and  from  spring  frosts  and  ripen  their 
fruit  from  one  to  two  weeks  earlier  than  those  planted  on 
the  land  along  the  "rim  rock"  or  at  a  distance  from  the  can- 
yon. This  phenomenon  is  explained  by  the  fact  that  the 
rocks  of  the  canj^on  walls  hold  the  heat,  are  dark  colored  and 
hence  absorb  a  maximum  of  the  sun's  rays,  and  that  there 
is  a  "draw"  of  air  down  the  canyon  that  wards  off  frosty 
conditions. 

243.  Winds. — While  winds  play  an  important  role  in 
frost  prevention,  they  also  are  a  factor  in  augmenting  win- 
on  the  coast.  Yet  in  the  severe  winter  of  1917-18,  the  effect  of  the 
water  was  insufficient  to  prevent  the  winter-killing  of  a  well-cared-for 
young  orchard  within  sight  of  the  open  water.  The  slope  was  a  gentle 
one  to  the  coast  line,  yet  such  hardy  varieties  as  Wealthy  and  Mcintosh 
were  killed  as  readily  as  the  tender  ones,  such  as  Baldwin  and  Wagener. 
The  ground  was  bare  at  the  time  of  the  low  temperature  in  December, 
and  hence  the  root-killing  was  extensive. 


274  POMOLOGY 

ter  injury  in  some  sections.  Frequently  high  wind  velocity 
will  accompany  low  temperatures  and  if  the  soil  is  not  well 
protected  by  a  covering  of  snow  or  of  vegetation,  it  will 
diy  out  to  the  point  at  which  root  injury  is  extensive.  The 
twigs  and  buds  may  also  be  injured  to  a  greater  extent  under 
such  conditions,  and  it  is  connnonly  supposed  that  their 
tissues  are  directly  dried  out  by  the  action  of  the  wind.  It 
is  more  probable,  however,  that  these  tissues  experience  a 
drying  to  death  due  to  the  water  supply  being  shut  off  by 
the  freezing  of  the  roots. 

ORCHARD   PRACTICES 

244.  Cultivation.^ — As  indicated  above,  the  chief  factor 
in  hardiness  of  fruit-trees  is  their  maturity  before  going  into 
winter  condition.  Therefore,  in  sections  in  which  winter 
injury  is  likely  to  occur,  the  orchard  practices  should  be 
such  as  to  obtain  a  good  growth  and  yet  allow  the  wood  and 
buds  to  mature  before  winter.  In  a  cultivated  orchard  the 
tillage  should  stop  by  the  first  or  middle  of  July  in  most  dis- 
tricts (except  when  it  is  an  advantage  to  delay  the  rest- 
period).  A  cover-crop  should  also  be  sown  at  the  time  of 
the  last  cultivation  as  it  has  a  twofold  function  in  relation 
to  winter  injury,  (1)  by  sei^ving  to  withdraw  any  excess  mois- 
ture in  the  soil  and  hence  aid  in  maturity  of  the  trees;  and  (2) 
by  acting  as  a  mulch  to  prevent  such  deep  freezing,  and  al- 
ternate freezing  and  thawing  as  would  occur  if  the  land  were 
bare.  Emerson  ^  and  others  note  the  effects  of  various 
cover-crops  on  depth  of  freezing  in  orchards.  They  show 
that  in  a  season  of  snowfall  corn  or  cane  is  a  good  crop  for 
the  orchard  as  it  holds  the  snow  to  good  advantage,  while 
in  a  season  of  no  snow  such  crops  as  mat  down  well  will  af- 
ford the  greatest  protection. 

1  Neb.  Agr.  Exp.  Sta.  Bull.  92.     1906. 


WINTER  INJURY 
Table  LXXXII 

DEPTH    OF    FREEZING    (AFTER  EMERSON) 


275 


vVo  snow 

Heavy  snow 

Depth  of  snow 

Depth  of  freezing 

Cornstalks 

17  in. 

18  in. 

G  in. 

Clean  cultivation 

19   " 

2   " 

24   " 

Oats 

12   " 

12   " 

12   " 

Millet 

12   " 

12   " 

15   " 

245.  Pruning. — Not  much  can  be  said  in  regard  to  the 
relation  of  pruning  to  winter  injuiy  except  what  has  already 
been  stated,  namely,  that  practices  which  maintain  a  strong 
vigorous  tree  and  yet  permit  normal  maturity  are  likely 
to  reduce  danger  from  winter  injury.  At  the  Missouri 
Experiment  Station  it  was  found  that  the  vigor  and  rela- 
tively late  growth  caused  by  stimulation  of  peach  trees 
would  have  some  effect  in  reducing  bud  injury  in  the  spring. 
This  was  due  to  the  shifting  of  the  rest-period  to  later  in 
the  season,  as  indicated  before.  "In  Missouri  nearly  every 
winter  warm  weather  starts  the  buds  into  growth  more  or 
less.  Fruit-buds  on  trees  that  have  made  a  vigorous  growth, 
caused  by  reasonably  severe  heading  back  or  by  cultivation, 
are  the  less  liable  to  winter  injury."  ^ 

If,  however,  the  injuiy  has  taken  place,  it  becomes  im- 
portant to  prune  judiciously  if  the  best  response  is  to  be 
obtained.  If  peach  trees  have  been  severely  frozen  in  the 
wood,  it  is  best  to  give  them  a  moderate  pruning.  If  such 
trees  are  severely  pruned  (leaving  only  bases  of  the  main 
limbs),  they  are  very  likely  to  be  killed,  but  if  the  same  trees 
1  Mo.  Agr.  Exp.  Sta.  BuU.  74. 


276  POMOLOGY 

are  moderately  pruned,  experience  shows  that  the  maximum 
number  can  be  saved. ^    (See  Plate  VIII  b.) 

246.  Protecting  trees  and  buds. — Various  efforts  have 
been  made  to  protect  tender  trees  and  their  buds  during  the 
winter,  with  some  degree  of  success.  Such  precautions  are 
of  special  value  in  sections  in  which  growth  is  likely  to  be 
excited  by  premature  warm  spells,  followed  by  low  tem- 
peratures. 

When  the  wood  or  buds  are  likely  to  be  frozen  during  the 
winter  season  while  they  are  entirely  dormant,  the  only  prac- 
tice that  seems  efficient  is  to  layer  the  vines  or  trees  entirely, 
and  this  is  not  often  feasible.  Some  peach  orchardists  do, 
however,  cut  the  roots  on  one  side  of  the  tree,  pull  it  down 
into  a  trench  and  cover  it  with  soil,  which  has  prevented 
injury.  Entire  grape  vineyards  are  also  laid  down  and  cov- 
ered with  soil,  with  success." 

Baling  the  trees  with  hay,  straw,  or  other  material  has  also 
been  practiced  with  success,  but  is  not  generally  recom- 
mended. 

Chief  among  the  experimental  efforts  to  coat  the  trees 
and  buds  with  a  protective  material  is  the  work  of  Whitten.^ 
He  observed  that  the  chief  damage  to  the  peach  in  Mis- 
souri resulted  from  killing  after  the  trees  had  been  started 
into  premature  growth  from  unseasonable  weather  in  the 
winter  or  early  spring.  As  a  means  to  prevent  the  swelling 
of  the  buds,  the  following  treatment  was  given:  "During 
the  winter  a  row  of  peach  trees,  running  diagonally  across 
the  orchard,  so  as  to  embrace  several  varieties,  was  whitened 
by  spraying  with  a  lime  white  wash.  These  trees  had  been 
set  only  two  years  and  had  but  few  fruit-buds.    Four  older 

1  Mo.  Agr.  Exp.  Sta.  Bull.  55.    1902. 

^Hedrick,  U.  P.  Proc.  Amer.  Pom.  Soc,  35  Bienn.  Rept.  1917. 
p.  48. 

3  Whitten,  J.  C.    Mo.  Agr.  Exp.  Sta.  Bull.  38.    1897. 


WINTER  INJURY 


277 


trees,  in  various  parts  of  the  grounds,  were  also  whitened." 
The  following  table  gives  the  results  on  time  of  blooming: 

Table  LXXXIII 

effect  of  whitewashing  peach  trees  to  delay  bloom 
(after  whitten) 


Varu'ty 

TreulmeHt 

First  flower 

Full  bloom 

Last  bloom 

Health  Cling 

Whitened 

Not 

April  13 
"     11 

April  21 
"    IS 

April  29 

"    27 

Wonderful 

Whitened 

Not 

"     14 
"     11 

"    22 
"    18 

"    29 
"    25 

Rivers  Early 

Whitened 
Not 

"     13 

"       9 

"    21 

"    29 

"    27 

Silver  Medal 

Whitened 
Not 

"     13 

"      7 

"    18 
"     13 

"    28 
"    21 

As  a  more  striking  effect  of  the  winter  on  the  treated  and 
untreated  trees,  it  is  recorded  that  80  per  cent  of  whitened 
buds  passed  the  winter  safely  when  only  20  per  cent  of  the 
unwhitened  ones  were  unharmed. 

A  very  interesting  set  of  experiments  was  conducted  to 
illustrate  the  difference  in  absorption  of  heat  between  white 
and  colored  material.  Thermometers  were  covered  with 
various  colored  cloth  and  whitewash  and  exposed  in  the 
orchard  and  on  the  side  of  a  building.  When  the  sun  was 
not  shining  the  thennometers  registered  much  the  same, 
but  when  the  sunlight  was  intense  marked  differences  oc- 
curred. "At  one  time,  during  bright  sunshine  a  difference 
of  21  degrees  was  recorded  between  the  white  covered  and 
the  purple  covered  thermometers.  A  difference  of  10  to  15 
degrees  was  frequently  noted  between  these  two.  This  is 
sufficient  to  indicate  that  we  might  expect  considerable  dif- 


278  POMOLOGY 

ference  in  the  growth  and  time  of  flowering  of  whitened  and 
unwhitened  peach  trees." 

247.  Securing  hardier  fruits. — A  discussion  of  breeding 
hardier  fruits  is  included  in  the  general  subject  of  breeding 
(Chapter  XIII),  but  a  statement  in  regard  to  the  acclimati- 
zation of  plants  is  apropos  at  this  point.  There  is  a  lack  of 
unity  of  opinion  on  this  point,  although  it  has  been  discussed 
for  many  years  a,nd  many  observations  have  been  recorded. 
It  seems  unlikely  that  individuals  of  a  tender  species  will 
manifest  any  permanent  character  for  hardiness  when  such 
plants  are  removed  to  a  colder  climate.  While  an  occasional 
individual  may  be  more  resistant  to  cold  than  its  companions 
of  the  same  origin,  the  enviromnent  may  be  different  or  some 
other  cause  operating  which  would  not  be  permanent.  To  at- 
tempt to  select  biotypes  showing  this  hardy  character  would 
be  a  slow  process  with  the  weight  of  evidence  against  its  suc- 
cess. The  better  procedure  to  follow  would  be  to  breed  such 
tender  species  with  hardy  "relatives"  and  select  individuals 
exhibiting  the  desirable  qualities  of  both  parents.  Hence  it 
is  practically  useless  to  attempt  to  find  a  particularly  hardy 
Baldwin  apple  or  Crawford  peach  tree  from  which  to  prop- 
agate a  strain  that  will  withstand  the  northern  winters  where 
these  varieties  are  unreliable. 

248.  Treatment  of  frozen  trees. — Great  care  must  be 
exercised  in  treating  trees  which  have  been  frozen  or  the 
injury  may  be  extended  rather  than  reduced.  As  indicated 
previously,  the  pruning  given  winter-injured  trees  calls  for 
moderation  and  the  operation  should  not  be  hastened  but 
rather  delayed  until  the  probable  injury  can  be  determined. 
Some  seasons  the  peach  is  so  injured  that  the  buds  are  de- 
layed in  starting;  this  calls  for  careful  observation  lest  live 
wood  be  cut  away  and  the  tree  umiecessarily  reduced. 

In  addition  to  proper  pruning,  it  is  also  advantageous  to 
apply  a  quickly  available  form  of  nitrogen,  such  as  nitrate 


WINTER  INJURY  279 

of  soda  or  sulfate  of  ammonia,  as  a  means  of  stimulating 
growth.  Thorough  cultivation  should,  of  course,  be  followed 
when  conditions  permit. 

Special  repair  work  may  also  be  necessary,  such  as  bridge- 
grafting  and  cleaning  and  disinfection  of  the  wounds.^ 

249.  Variation  in  hardiness  of  fruits. — While  the  vari- 
eties within  any  given  kind  of  fruit  vary  widely  in  hardiness, 
yet  there  is  a  rather  marked  difference  between  species  and 
genera  of  the  common  fruits.  The  apples  as  a  class  are  the 
most  hard}''  of  the  commonly  grown  tree-fruits,  followed  by 
the  American  plums,  Japanese  plum,  sour  cheriy,  European 
plum,  pear,  sweet  cheriy,  apricot,  and  peach.  It  is  true 
that  the  currant  and  gooseberry  and  certain  species  of  Amer- 
ican plums  are  more  hardy  than  the  apples.  There  is  so 
much  variation  in  different  localities  and  in  different  sea- 
sons, however,  that  such  a  classification  cannot  be  con- 
sistent. 

250.  Hardy  and  tender  varieties, — As  with  the  different 
s])ocies  and  genera,  so  the  varieties  of  fruits  are  variable  in 
hardiness,  depending  on  a  multitude  of  conditions.^  The 
following  lists  are  an  attempt  to  rate  some  of  the  more  com- 
monly grown  varieties,  the  hardiest  being  in  the  first  column 
and  those  in  the  other  columns  decreasingly  hardy. 

1  Purdue  Univ.  Agr.  Exp.  Sta.  Circ.  87.     1918. 

-  XI.  S.  Dept.  Agr.  Bur.  Plant  Ind.  Bull.  151.  1909.  Fruits  recom- 
mended by  the  American  Pomological  Society  for  cultivation  in  the 
various  sections  of  U.  S.  and  Canada. 


280 


POMOLOGY 


RELATIVE  HARDINESS  OF  SOME  COMMON  VARIETIES  OF  FRUIT 
APPLE    (hardiness   IN   WOOD) 


1                     2 

3 

4 

5 

Hibernal       Wealthy      Northern  Spy 

Ben  Davis 

Baldwin 

Ontario         Fameuse     Red  Canada 

Gano 

R.  I.  Greening 

Mcintosh      Delicious    Rome 

Jonathan 

King 

Oldenburg    N.  W 

Wagener 

Hubbardston 

Tolman             Greening 

Twenty  Ounce 

Gravenstein 

Yellow           Wolf  River 

Grimes 

Fall  Pippin 

Transparent 

Winesap 

Stayman 

Red  Astra-    Pewaukee 

York  Imperial 

Black  GiUi- 

chan 

flower 

Haas 

Malinda 

Patten  Greening 

peaoh  (hardiness  in  bud) 

1 

2 

3 

4 

Crosby 

Champion 

Elberta  (hardy 

Crawford  (early 

Rochester 

Georgia  (Belle  of) 

in  wood) 

and  late) 

Hill's  ChiU 

Carman 

St.  Johns 

Chairs  Choice 

Gold  Drop 

Waddell 

Mt.  Rose 

Niagara 

Wager 

Alton 

Foster 

J.  H.  Hale 

Stevens  Rareripe 

Ray 

Surprise 

Greensboro 

Hiley 

Salway 

Lemon  Free 

Kalamazoo 

Reeves 

Fitzgerald 

Bernard 
Triumph 
Smock 

Fox  Seedling 

CHERRY    (hardiness   IN   WOOD) 


Windsor 
Eugenia 
May  Duke 
Late  Duke 
Early  Richmond 
Tartarian 
English  Morello 
Ostheim 
Vladimir 


Montmorency 


Reine  Hortense 
Schmidt 
Governor  Wood 


WIXTER  IX JURY  281 

PEAR  (hardiness  IN  WOOD) 

1  2 

Flemish  Beauty  Angouleme 

Anjou  Bartlett 

Sheldon  Bosc 

Seckel  Clairgeau 

Tyson  KieflFer 

Longworth  Clapp  Favorite 
Winter  Nelis 
Orel 

251.  The  grape. — With  the  grape  as  with  other  fruits 
the  chief  factor  affecting  its  harcUness  is  maturity.  Glad- 
win ^  shows  that  the  length  of  the  growing  season  has  a  de- 
cided effect  on  the  subsequent  wintering  of  the  vines.  Not 
only  does  a  longer  growing  season  permit  greater  maturity 
of  the  canes  and  an  increased  thickness  of  the  cell-walls  of 
the  wood  tissue,  but  it  also  permits  the  ripening  of  the  fruit 
which  bears  a  correlation  to  the  maturity  of  the  canes.  He 
says,  "Our  observations  during  the  years  1915-16  indicate 
quite  clearly  that  until  an  actual  freeze  occurs  the  vine  ex- 
tends its  energies  to  maturation  of  its  fmit  at  the  expense  of 
wood  maturity;  and  if  the  umnpe  fmit  be  allowed  to  hang 
throughout  the  fall,  wood  maturity  is  not  nearly  so  complete 
as  when  the  fruit  is  picked  some  time  previous  to  a  freeze." 

It  is  also  pointed  out  that  the  incipient  floral  parts  within 
the  complex  bud  of  the  grape  may  be  destroyed  by  low  tem- 
peratures and  hence  result  in  an  "off  year."  This  is  often 
erroneously  accredited  to  a  hea\^  crop  the  previous  season 
having  robbed  the  buds  of  sufficient  nutrient  material  to 
pennit  fruit-buds  to  form. 

The  application  of  such  fertilizing  materials  as  nitrogen, 
phosphorus,  and  potassimn  had  no  appreciable  effect  on  the 
killing  of  grape  vines. 

1  N.  Y.  Agr.  Exp.  Sta.  Bull.  433.    1917. 


CHAPTER  XII 
POLLINATION  AND  THE  STERILITY  PROBLEM 

The  sexual  relation  of  plants  and  the  union  of  male  and 
female  elements  to  the  proper  development  of  fruits  have 
been  known  since  ancient  times,  but  it  is  only  within  the 
past  quarter  of  a  century  that  marked  progress  has  been 
made  in  understanding  the  causes  of  these  phenomena  and 
many  of  them  are  not  yet  fully  apprehended.  In  studying  the 
effect  of  pollination  on  the  setting  of  orchard  fruits,  one 
should  keep  in  mind  that  two  points  are  involved:  first,  the 
importance  of  pollinization  in  effecting  the  development  of 
fruits  even  though  no  actual  fertilization  takes  place;  and 
second,  that  as  a  result  of  such  pollination  there  may  be 
fertilization  and  development  of  the  embryo,  resulting  in 
viable  seed  capable  of  producing  new  progeny.  From  the 
standpoint  of  the  breeder,  the  latter  is  paramount  (i.  e.,  the 
production  of  fertile  seeds),  but  the  orchardist  is  concerned 
primarily  with  the  former  of  the  two  results.  The  vegetable- 
grower,  on  the  other  hand,  may  be  interested  in  the  pro- 
duction of  viable  seed,  depending  on  the  crop  involved, 
and  with  the  nut-grower,  it  likewise  becomes  a  matter  of 
practical  importance. 

252.  Investigations  in  pollination. — Centuries  prior  to 
the  Christian  era,  the  peoples  of  Egypt  and  Mesopotamia 
were  cultivating  dioecious  plants  for  food  and  practicing 
artificial  pollination  of  the  fig  and  date  palm.^  However,  the 
first  scientific  investigation  of  this  problem  was  not  forth- 
coming until  A.  D.  1694  when  Camerarius  proved  that  fer- 

1  Johnson,  D.  S.    Sexuality  in  plants.    Jour.  Heredity,  6:  3-16.    1915. 

282 


POLLINATION  AND  STERILITY  283 

tile  seeds  are  not  produced  if  the  pollen  or  male  element  is 
lacking  or  unavailable  when  the  flowers  are  in  bloom.  This 
has  later  been  observed  for  angiosperms  in  general.  Other 
subsequent  investigators  made  contributions  on  this  prob- 
lem, but  the  work  of  Sprengel  of  Germany  (1793)  marked 
an  epoch  when  he  published  "The  Secret  of  Nature  in  the 
Form  and  Fertilization  of  Flowers  Discovered."  His  con- 
temporary in  England,  Thomas  Andrew  Knight,  published 
a  number  of  articles  bearing  on  the  pollination  question  and, 
as  a  matter  of  fact,  almost  discovered  "Mendelism,"  and 
he  announced  as  a  law  that  "in  no  plant  does  self-fertiliza- 
tion occur  for  an  unlimited  immber  of  generations."  This 
idea  found  its  great  culmination  in  Darwin's  work  when  he 
said  "nature  abhors  self-fertilization."  And  yet  notwith- 
standing the  wide  application  which  this  principle  may  have, 
it  is  by  no  means  universal.  Wheat,  for  example,  is  self- 
fertile,  likewise  peach  varieties  in  general,  the  cleistogamous 
flowers  of  violet  never  open,  the  tomato  is  regularly  self- 
fertilized,  and  so  with  many  other  plants. 

In  this  country  a  great  impetus  was  given  to  a  careful 
study  of  the  inter-relations  of  varieties  of  any  kind  of  fruit 
in  an  orchard  plantation  by  the  works  of  Beach, ^  Waite,- 
and  Waugh.^ 

The  problems  of  pollination  incident  to  the  setting  of 
fruit  will  be  considered  in  this  connection,  but  the  study  of 
cross-pollination  for  the  purpose  of  producing  new  varieties 
will  be  discussed  in  the  next  chapter. 

253.  Causes  of  unfruitfulness. — Many  diverse  reasons 
or  causes  must  be  given  for  the  failure  of  trees  to  produce 
fruit.    Some  cases  of  barrenness  still  lack  explanation.    The 

'  Beach,  S.  A.    Rept.  N.  Y.  State  Agr.  Exp.  Sta.    1892,  '94,  '95,  '98, 
'99,  1900,  '02. 
nVaite,  M.S.    U.  S.  Dept.  Agr.,  Div.  Veg.  Path.  Bull.  5.    1894. 
3  Waugh,  F.  A.    Rept.  Vt.  Agr.  Exp.  Sta.    1896,  '97,  '98,  1900. 


284  POMOLOGY 

following  may  be  listed  as  the  more  common  causes:  failure 
of  fruit-buds  to  develop;  lack  of  vigor  or  excessive  vigor  re- 
sulting in  the  dropping  of  the  expanded  flowers;  winter  in- 
jury to  the  floral  parts;  frost  at  blossoming  time  resulting 
in  injury  to  flowers  or  inactivity  of  pollen-cany ing  insects 
and  the  consequent  lack  of  pollination;  lack  of  "affinity" 
between  varieties  (self-  or  inter-sterility);  defective  pollen 
or  embryo  sacs;  or  hybridity,  the  causes  of  which  are  not 
understood. 

Some  of  these  factors  are  treated  elsewhere  and  only  the 
various  problems  having  to  do  with  pollination  and  sterility 
will  be  considered  at  this  time. 

254.  Development  of  pollen.^ — The  pollen  produced 
within  the  anther-sacs  of  the  stamens  contains  the  male  ele- 
ment of  the  reproductive  system  of  flowering  plants.  A 
brief  statement  of  the  development  of  the  pollen  will  more 
clearly  introduce  the  problems  encountered  in  a  study  of 
pollination.  A  sufficient  similarity  exists  between  the  several 
tree-fruits  that  all  need  not  be  considered. 

The  stamens,  as  indicated  in  Chapter  III,  originate  as 
an  outgrowth  from  the  torus,  differentiating  in  their  devel- 
opment into  filaments  and  anthers.  The  anthers  consist 
essentially  of  four  lobes  of  pollen-forming  tissue  which,  on 
further  development,  become  differentiated  as  four  sacs  or 
locules,  each  of  which  contains  the  pollen-grains,  one  sac 
corresponding  to  each  lobe.  In  the  early  development  of 
the  anther,  the  sporogenous  tissue  is  first  seen  within  each 
lobe,  and  surrounding  the  future  ''pollen-making"  tissue  is 
a  layer  of  cells  known  as  the  tapetum.  The  cells  within 
the  tapetum  become  the  mother  cells  which,  on  further  di- 

1  See  Sandsten,  E.  P.  Wis.  Agr.  Exp.  Sta.  Res.  Bull.  4.  1909.  Kraus, 
E.  J.  Ore.  Agr.  Exp.  Sta.  Res.  Bull.  1,  Part  1.  1913.  Dorsey,  M.  J. 
Minn.  Agr.  Exp.  Sta.  Bull.  144.  1914.  Black,  C.  A.  N.  H.  Agr.  Exp. 
Sta.  Tech.  Bull.  10.     1916. 


POLLINATION  AND  STERILITY  285 

vision  (reduction  division) ,  become  the  microspores  or  pollen- 
grains.  Usually  the  anthers  are  partially  developed  prior 
to  winter  of  the  season  before  the  blossom  opens.  If  the 
development  has  gone  sufficiently  far  in  the  autumn  so' 
that  the  first  division  of  the  cells  in  spring  is  the  reduction 
division,  then  they  are  in  the  pollen  mother  cell  stage  at 
that  time.  However,  they  may  or  may  not  have  reached 
that  point  in  the  autumn.  When  growth  is  resumed  in  the 
spring,  cell  division  becomes  active  and  pollen-grains  are 
eventually  formed.  The  pollen-grains  are  unicellular  and 
are  known  botanically  as  microspores,  each  one  finally  devel- 
oping two  male  gametes.  The  pollen-grain  has  a  covering  of 
two  layers,  the  outer  of  which  in  some  plants  is  frequently 
oily,  gelatinous,  or  possessing  minute  projections  useful  in  aid- 
ing in  its  distribution.  This  latter  adaptation,  however,  is  not 
encountered  with  common  fruits.  When  "ripe"  or  mature, 
the  anthers  dehisce  or  expose  the  pollen-grains  and  on  trans- 
fer to  a  receptive  stigma,  the  latter  germinate,  as  later  de- 
scribed. If  conditions  are  favorable  and  the  two  tissues  are 
"congenial,"  fertiUzation  takes  place. 

A  similar  development  occurs  with  grape  pollen  as  for  pol- 
len in  general.  It  has  been  shown  that  a  fundamental  de- 
fect may  occur  in  its  development  which  accounts  for  ste- 
rility in  the  grape  as  is  described  later. 

255.  Germination  of  the  pollen. — The  condition  of  the 
stigma  when  it  becomes  receptive  or  at  the  time  of  pollination 
should  next  receive  attention.  The  stigmatic  surface  just 
prior  to  the  receptive  period  has  a  velvety  papillose  appear- 
ance which  is  readily  distinguished  from  the  moist  often 
viscid  condition  when  it  is  receptive.  When  the  pollen- 
grains  reach  the  receptive  stigma,  they  are  surrounded  by 
the  stigmatic  fluid  which  has  been  secreted  and  in  which 
the  pollen  gemiinates. 

It  has  been  shown  that  sunshine  had  little  or  no  effect  on 


286 


POMOLOGY 


the  germination  of  apple  and  plum  pollen,  or  on  the  rate  of 
growth  of  the  pollen-tube.  These  tests  refer  to  the  artifi- 
ficial  germination  of  pollen-grains  in  various  media.  It  is  well 
known  that  blossoms  will  be  fertilized  and  the  petals  fall 
much  more  quickly  in  bright  than  in  cloudy  weather.  The 
following  data  support  the  above  conclusions  in  regard  to 
germination : 

Table  LXXXIV 
percentage  of  germination  and  rate  of  growth  of  pollen  in 

SUNSHINE  AND  CLOUDINESS    (aFTER  SANDSTEN) 


Primus 
americana 

Apple  (Pyrus 
Mains) 

Primus 
domestica 

Temperature,  degrees  C 

34 

31 

33 

33 

32 

33 

32' 

30' 

331 

70 

68 

69 

71 

68 

69 

62 

60 

64 

72 

67 

70 

70 

70 

68 

60 

59 

65 

The  rate  of  growth  of  the  pollen-tube  appears  to  be  read- 
ily affected  by  low  temperature  and,  therefore,  actual  fer- 
tilization may  be  delayed  some  seasons  more  than  others 
by  several  days.  Sandsten  reported  that  "Under  favorable 
conditions  it  requires  nine  to  thirty-two  hours  for  the  pollen 
tube  of  apples,  plums,  and  cherries  to  reach  the  ovary  when 
placed  on  the  stigma  or  in  the  germinating  medium.  Cherry 
pollen  requires  a  little  over  12  hours.  Two  or  three  bright 
days  at  the  time  of  full  bloom  is  sufficient  for  the  setting  of 
the  fruit."  Dorsey  questions  these  observations  in  regard 
to  the  plum  and  thinks  the  time  would  be  greater,  as  much 
as  eight  to  ten  days  under  some  conditions. 

Goff  has  shown  that  "Plum  pollen  does  not  germinate 
at  temperatures  below  40°  F.,  and  even  at  temperatures  as 
high  as  51°  F.  that  there  is  slow  pollen  tube  growth." 
'  Medium,  a  3  per  cent  cane-sugar  solution. 


POLLINATION  AND  STERILITY 


287 


256.  Longevity  and  viability  of  pollen. — At  present  there 
is  considerable  difference  of  opinion  in  regard  to  tlie  lengtli 
of  time  pollen  remains  viable.  One  investigator  ^  records 
interesting  observations  on  the  longevity  of  pollen  secured 
from  widely  different  sources,  namely,  Washington  (state), 
Tennessee,  Missouri,  and  Mimiesota.  Part  of  the  samples 
were  on  the  road  four  to  five  daj^s  but  arrived  in  "perfect 
condition."  Germination  tests  on  its  arrival  showed  all 
samples  to  be  practically  normal.  It  was  then  placed  in  the 
laboratoiy  in  a  temperature  ranging  from  10°  to  18°  C, 
and  tests  were  made  each  month  for  six  months  with 
the  exception  of  the  last,  which  was  eight  months  after 
its  arrival.  The  following  data  show  the  results  of  this 
test: 


Table  LXXXV 

LONGEVITY  OF  APPLE  AND  PLUM  POLLEN.       (AFTER  SANDSTEN) 


First 

Lois 

germt- 
tuition 

Second 

Third 

Fourth 

Fifth 

Sixth 

Seventh 

Per 

Per 

Per 

Per 

Per 

Per 

Per 

cent 

cent 

cent 

cent 

cent 

cent 

cent 

1 

Apple 

47 

43 

44 

38 

39 

38 

12 

Plum 

53 

52 

42 

35 

30 

18 

0 

2 

Apple 

58 

57 

50 

43 

38 

33 

10 

Plum 

54 

48 

38 

26 

21 

11 

0 

3 

Apple 

42 

46 

40 

38 

39 

19 

5 

Plum 

60 

48 

42 

25 

18 

2 

0 

4 

Ai)pIo 

56 

51 

52 

40 

23 

28 

8 

Plum 

50 

47 

38 

20 

12 

0 

0 

Sandsten,  E.  P.    Wis.  Agr.  Exp.  Sta.  Tech.  Bull.  4.    1909. 


288  POMOLOGY 

The  work  of  Crandall,^  however,  indicates  that  apple  pol- 
len may  not  remain  viable  so  long  as  indicated  by  Sandsten. 
After  observations  for  three  seasons,  he  shows  that  when 
pollen  was  used  that  varied  in  age  from  one  to  eleven  days, 
"The  percentages  indicate  no  definite  relation  between  age 
of  pollen  and  success  obtained.  .  .  .  Apple  pollen  one  month 
old  has  been  tested  several  times  in  drop  cultures,  but  no 
germination  took  place."  He  quotes  Pfundt  as  finding  that 
the  pollen  of  Pijrus  Mains  (presumably  the  wild  apple  of 
Europe)  retained  its  vitality  in  diy  air  for  thirty-eight  days 
and  when  preserved  over  sulfuric  acid,  for  seventy  days. 
"Records  at  the  Illinois  station  contain  no  evidence  of  du- 
ration of  vitality  beyond  the  fairly  successful  use  of  pollen 
of  Mains  mains  when  eleven  days  old."  Another  investi- 
gator reports  that  a  few  pollen-grains  of  apple  germinated 
after  nearly  three  months  and  of  pear  after  two  months, 
but  no  tests  were  made  after  longer  periods  than  these.^ 
Sweet  cherry  pollen  also  has  a  reasonably  long  period  in 
which  it  is  viable,  as  germination  tests  showed  it  to  be  in  as 
good  condition  three  weeks  after  it  was  gathered  and  dried 
as  when  it  was  first  collected.^ 

Further  data  show  that  pollen  is  not  injured  by  a  temper- 
ature ranging  from  25°  to  55°  C,  if  it  be  dry,  but  "at  a  tem- 
perature of  40  to  50  degrees  C,  in  a  saturated  atmosphere, 
the  pollen  grains  burst  open  due  to  the  rapid  inhibition  of 
water  and  the  number  of  bursted  pollen  grains  increased  as  the 
temperature  increased.  Freezing  temperatures  ranging  from 
—  1.5  to  —  1  degree  C.  were  not  seriously  injurious  to  the  pol- 
len of  apple,  pear,  and  plum  while  less  than  50  per  cent  of 

iCrandall,  C.  S.  The  vitality  of  pollen.  Soc.  Hort.  Sci.  1912. 
pp.  121-130. 

2  Adams,  J.  Germination  of  the  pollen  grains  of  apple  and  other 
fruit  trees.    Bot.  Gaz.  61:131-147.     1916. 

3  Ore.  Agr.  Exp.  Sta.  Bull.  116.    1913. 


POLLINATION  AND  STERILITY  289 

peach  and  apricot  pollen  grains  were  killed  by  this  tempera- 
ture." The  lack  of  cultivation  and  fertility  in  orchards 
greatly  injures  the  production  and  fertility  of  pollen. 

From  these  investigations  it  can  be  seen  that  the  pollen 
of  the  apple,  plum,  peach,  and  cheriy,  (and  it  can  be  added 
for  other  fruits  as  well)  will  remain  viable  throughout  the 
period  of  blooming  and  probal:)ly  for  a  much  longer  time  if 
kept  \mder  ordinary  conditions  of  temperature  and  humidity. 

257.  Length  of  receptive  condition  of  the  stigma. — In 
contrast  to  the  surprisingly  long  time  that  pollen  is  viable 
and  capable  of  germination  and  to  the  untoward  conditions 
that  it  can  withstand,  the  ]iistils  are  most  delicate  and  of 
short  duration.  They  are  readily  susceptible  to  mechanical 
injury  as  well  as  to  damage  from  inclement  weather.  There 
is  some  question  as  to  whether  a  stigma  has  more  than  one 
period  of  active  secretion;  in  some  cases  there  is  only  one, 
while  other  observers  have  held  that  more  than  one  occurs. 
The  pistils  are  sensitive  to  cold  and  are  often  injured  when 
other  floral  parts  are  unhurt.  Frosts  or  drying  winds  may 
cause  a  loss  of  the  whole  or  a  part  of  the  fruit  crop  if  they 
occur  when  the  blossoms  are  open. 

Waugh  ^  found  that  the  stigmas  of  plums  are  receptive 
"From  four  to  six  days  if  pollen  is  withheld  and  conditions 
are  favorable.  If  pollen  is  abundant  they  are  almost  im- 
mediately pollinated  and  cease  to  be  receptive."  Dorsey 
found  that  "under  normal  conditions,  the  plum  stigma  re- 
mains receptive  for  a  maximum  period  of  about  one  week, 
but  usually  from  four  to  six  days." 

258.  Fertilization. — The  process  of  fertilization  may  be 
briefly  stated  in  this  connection  since  the  whole  problem  of 
fertility  and  sterility  of  orchard  fruits  is  intimately  associa- 
ted with  it.  When  the  pollen-grain  or  microspore  is  formed, 
it  possesses  two  nuclei,  one  known  as  the  tube  (vegetative) 

1  Vt.  Agr.  Exp.  Sta.  11th  Ann.  Rept.    1897-1898.    p.  258. 


290 


POMOLOGY 


nucleus  and  the  other  the  generative  nucleus.  When  the 
pollen-grain  germinates  the  latter  nucleus  divides,  forming 
two  sperm  or  male  nuclei. 

As  the  pollen-tube  grows  down  the  style  of  the  pistil,  the 
male  nuclei  as  well  as  the  tube  nucleus  continue  to  approach 
the  embiyo  sac  in  which  are  the  ovules.  Here  the  tip  of  the 
tube  enters  the  micropyl  and  dis- 
charges the  two  nuclei  into  the  em- 
bryo sac  so  that  fusion  may  take 
place,  one  with  the  egg  or  female 
nucleus  and  the 
other  with  the 
primaiy 


pericarp^_^ 


pollen   tube 


synergids 

e^g  nucleus 


nucellus  

embryo  sac  -  - ' ' 

polar  nuclei*-' 

anti  podals  -^"-'^ 


Fig.  36. — Diagram  of  a  simple  pistil  as  seen  in 
lengthwise  section,  showing  a  single  ovule 
just  prior  to  fertilization. 


,  outer  Integument 
sperm  nucleus,  inner  Integumen 
Hence  it  is  seen 
that  two  ferti- 
lizations take 
place,  one  hav- 
ing to  do  with 
the  origin  of  a 
new  seed  (ovule) 
and  the  other 
with  the  devel- 
opment of  the  endosperm  or  food-storage  tissue  surrounding 
the  germ  within  the  seed.  As  is  well  known  from  a  study 
of  an  immediate  cross  between  field  and  sweet  com,  there 
is  an  effect  on  the  endosperm  of  the  first  or  immediate 
generation.  This  effect  may  be  seen  in  the  condition  of  the 
kernel,  i.  e.,  when  it  is  wrinkled  or  smooth  or  in  the  color 
of  the  endosperm  or  in  both. 

In  a  study  of  sterility  of  the  common  fruits  (as  well  as 
many  other  plants),  it  will  be  seen  that  not  infrequently 
the  endosperm  will  develop  but  the  embryo  will  perish,  a 
phenomenon  termed  embiyo  abortion.     (Fig.  36.) 


POLLINATION  AND  STERILITY  291 

259.  Cross-pollination. — The  experiments  of  Waite  and 
many  subsequent  workers  have  shown  that,  with  many- 
kinds  and  varieties  of  fruits,  it  is  necessary  to  have  a  trans- 
fer of  pollen  from  one  variety  to  another  in  order  to  insure 
fertilization  and  the  setting  of  fruit.  This  transfer  between 
varieties,  instead  of  from  the  stamens  to  the  pistils  of  the 
same  flower,  has  come  to  be  known  as  cross-pollination 
in  contradistinction  to  self-pollination.  That  cross-pollina- 
tion should  be  the  rule  with  many  fruits  will  be  shown 
later. 

In  selecting  a  pollinizer,  the  chief  concern  is  to  choose  a 
variety  that  possesses  the  following  characteristics: 

1.  It  must  blossom  at  the  same  time  and  preferably  at 
the  same  age  as  the  variety  which  is  to  be  pollinated. 

2.  It  must  be  inter-fertile  with  it. 

3.  Should  be  a  standard  variety,  i.  e.,  be  of  high  value 
for  the  purpose  grown. 

4.  Should  \)c  a  good  ]wllon-producer. 

260.  Means  of  effecting  cross-pollination. — Two  agencies 
have  usually  been  considered  instrumental  in  the  transfer 
of  pollen:  wind  and  insects.  Experimental  work  and  exten- 
sive observation,  however,  have  shown  that  wind  is  of  little 
or  no  importance  with  the  tree-fruits,  the  nuts  being  ex- 
cepted. Insects  play  a  most  vital  part  in  pollinating  the 
blossoms.  Chief  among  the  insects  are  the  bees,  particu- 
larly the  honey  bees. 

Nature  has  provided  for  the  visitation  of  insects  in  a  most 
conspicuous  way.  Students  of  nature,  particularly  Darwin 
and  his  followers,  are  in  full  agreement  that  the  insects  are 
attracted  by  the  bright  or  showy  flowers  and  by  the  nectar 
secreted  at  the  basal  parts,  thus  bringing  about  the  transfer 
of  the  pollen-grains  which  adhere  to  them,  from  flower  to 
flower.  When  the  flowers  are  so  constructed  as  to  permit 
pollination  by  the  wind,  they  are  said  to  be  anomophilous 


292  POMOLOGY 

and  when  insect  pollination  is  the  rule,  they  are  called  en- 
tomophilous. 

261.  Nature's   methods   of   avoiding    self-pollination.^ 

Several  means  have  been  developed  in  nature  to  prevent 
self-pollination.  Not  all  of  these  obtain  with  fruit-trees 
but  several  are  very  effective.  The  chief  devices  among 
flowering  plants  are: 

1.  Special  devices  or  contrivances  of  the  flower  which 
ensure  cross-pollination  when  insects  enter  the  flower.  Or- 
chids exhibit  these  adaptations  to  a  greater  degree  than  any 
other  group. 

2.  Difference  in  time  of  maturity  of  the  stamens  and  pis- 
tils. This  phenomenon  is  called  dichogamy.  When  they 
mature  simultaneously,  it  is  homogamy.  When  the  stamens 
precede  the  pistils  in  maturity,  it  is  termed  proterandrous, 
and  if  the  reverse  they  are  said  to  be  proterogynous. 

3.  Even  though  flowers  may  exhibit  homogamy,  the 
relative  position  of  the  pistils  and  stamens  or  their  rela- 
tive lengths  may  be  such  as  to  prevent  self-pollination. 
Such  a  condition  is  termed  kerkogamy  (dimorphous  of 
Darwin). 

4.  Separation  of  sexes.  With  most  fruits  the  flowers  are 
perfect,  i.  e.,  possess  both  stamens  and  pistils,  but  with  some 
forms  this  condition  does  not  exist.  The  strawberry  is  par- 
ticularly notorious  in  this  regard,  as  some  varieties  possess 
perfect  flowers  and  others  have  pistillate  flowers  only,  while 
others  which  are  perfect  have  more  or  less  abortive  and  hence 
worthless  stamens.  The  grape  also  exhibits  the  same  set  of 
conditions.  That  cross-pollination  is  necessary  under  such 
circumstances  appears  evident. 

262.  Effect  of  cross-pollination  on  the  fruit. — Entirely 
aside  from  the  results  of  cross-fertilization  on  the  off- 
spring, the  horticulturist  is  interested  in  any  effect  cross- 
pollination  would  have  on  the  somatic  tissue  of  the  fruit 


POLLINATION  AND  STERILITY  293 

which  immediately  develops.  The  experiments  seem  to  es- 
tablish rather  thoroughly  that  the  color  or  markings  of  a 
fruit  are  not  affected  by  the  pollen  used  in  fertilization, 
and  neither  is  the  flavor,  quality,  acidity,  or  "sweetness." 
That  some  of  these  characteristics  are  materially  changed  is 
sometimes  reported  but  they  do  not  seem  to  be  well  authen- 
ticated; at  least  such  changes  have  not  been  observed  under 
controlled  conditions.  Careful  observations  have  been  made 
to  determine  whether  color  of  fruit  could  be  modified  by  the 
pollen  parent.  The  conclusion  is  reached  that  color  in  the 
innnediate  cross  is  not  directly  influenced  by  the  kind  of 
pollen  used,  since  any  such  effect  must  be  found  within  the 
seed  (endosperm)  and  there  is  no  opportunity  for  an  influ- 
ence on  the  fleshy  portion. 

It  is  not  uncommon  to  see  fruits  in  which  the  color  shows 
distinct  "banding."  This  has  been  explained  as  a  somatic 
segregation  of  the  characters  for  color,  permitting  a  more  or 
less  independent  manifestation  of  them.  The  several  colors 
may  appear  as  bands  more  or  less  parallel  or  a  band  of  but 
one  color  surrounded  by  the  normal  color.  ^ 

The  results  reported  in  regard  to  size  and  shape,  however, 
are  not  in  harmony.  It  is  possible  that  under  varying  con- 
ditions the  outcome  may  be  different.  Fletcher  ^  states  that 
his  investigations  (mostly  with  apples  and  pears)  show  that 
there  is  "no  immediate  effect  of  pollen,  and  no  differences 
obviously  due  to  mutual  affinity.  The  cross-fertilized  fruits 
have  averaged  about  the  same  in  size,  shape,  color,  and 
quality  regardless  of  the  pollen  used."  Wicks  ^  comes  to  a 
similar  conclusion   from   his   studies  with   the  apple.     He 

^  For  further  details  see  Kraus,  E.  J.  "Bud  variation  in  relation  to 
fruit  markings."  Biennial  Crop  Pest  and  Horticultural  Report. 
1911-12.    Ore.  Agr.  Exp.  Sta. 

2  Va.  Agr.  Exp.  Sta.  Ann.  Kept.    1909-10.    pp.  213,  224. 

»Ark.  Agr.  Exp.  Sta.  Bull.  143  (Technical).     1918. 


294  POMOLOGY 

says,  "No  influence  of  the  male  pollen  of  any  variety  can 
be  detected  on  size,  color,  shape  and  quality  of  the  female 
parent." 

Alderman,'^  on  the  other  hand,  shows  a  decided  benefit 
from  cross-pollination  of  the  apple  over  blossoms  which  were 
"selfed"  or  crossed  with  pollen  from  a  tree  of  the  same  va- 
riety. A  summary  of  his  results  in  weight  of  fruit  as  affected 
by  pollination  is  here  given: 

Rome  Beauty  cross  Gain  over  selfed  27 . 8  per  cent 

York  Imperial  cross  Gain  over  selfed  42 . 7  per  cent 

Likewise,  Lewis  and  Vincent  found  an  improvement  in 
size  of  the  apple  from  cross-fertilization. 

These  latter  observations  are  in  line  with  the  original  in- 
vestigations of  Waite.  He  observed,  among  other  things, 
that  the  self-fertilized  Bartlett  pears  which  he  secured 
weighed  on  an  average  100.4  grams,  while  the  cross-fertil- 
ized pears  averaged  145.2  grams  each. 

263.  Effect  of  seed-bearing  on  the  fruit. — It  is  a  fact  of 
considerable  interest  that  there  is  commonly  a  correlation 
between  the  weight  of  seed  and  that  of  fruit.  This  of  course 
loses  force  in  the  case  of  parthenocarpic  fruits,  since  prac- 
tically no  seeds  are  developed.  Not  only  is  there  a  correla- 
tion in  regard  to  size  but  also  it  is  not  uncommon  to  find  a 
lack  of  full  development  in  a  portion  of  an  apple  or  pear 
where  no  seeds  have  matured  within  the  adhering  carpel  or 
carpels,  thus  giving  somewhat  one-sided  fruits.  This  phe- 
nomenon is  of  wide  application  and  may  often  be  seen,  for 
example,  on  examining  a  bean  pod  in  which  one  or  more 
ovules  did  not  develop,  resulting  in  a  hardened  constricture 
or  other  evidence  of  lack  of  development  of  the  parts  im- 
mediately surrounding  the  abortive  ovules.  In  such  cases, 
there  is  a  lack  of  stimulation  of  the  surrounding  parts  and, 
1  Proc.  Amer.  Soc.  Hort.  Sci.,  14th  Rept.     1917.     pp.  94-101. 


POLLINATION  AND  STERILITY  295 

as  no  development  of  the  seeds  takes  place,  the  fleshy  or 
surrounding  parts  usually  fail  to  develop  also. 

Not  only  is  there  an  influence  on  the  size  of  the  fruit,  but 
the  number  of  seeds  that  has  developed  may  also  affect  the 
quality,  the  more  seeds  the  higher  the  quality.  A  striking 
case  is  that  of  the  Japanese  persinunon  (Diospyros  Kaki)  ^ 
which  develops  many  parthenocarpic  fruits,  but  whether 
pollination  is  useful  as  a  stimulation  is  not  known.  The 
fruits  which  develop  seeds  manifest  a  richer  and  better  fla- 
vor than  the  seedless  ones,  and  also  other  marked  charac- 
teristics obtain.  The  seedless  fruits  are  larger  in  size,  of  a 
smoother  texture  and  usually  ripen  later  than  those  devel- 
oping seeds.  Outstanding  is  the  effect  of  the  seeds  on  the 
color  of  the  flesh.  When  seeds  develop,  the  flesh  is  dark  in 
color  and  light  when  seedless. 

Heinicke  records  the  relation  between  size  of  apples  and 
the  number  of  seeds  that  has  developed.  The  following 
fruits  of  Fallawater  apples  were  produced  on  spurs  of  equal 
vigor.- 

Number  of  seeds  Weight  grains  of  fruit 

3 16.84 

5 18.72 

8 23.15 

9 24.02 

11 29.40 

264.  Artificial  pollination. — The  artificial  pollination  of 
common  deciduous  fruit  blossoms  is  not  practiced  except 
for  experimental  piu'poses  or  the  production  of  new  varieties. 
Perhaps  the  nearest  approach  to  any  intervention  by  man 
is  the  occasional  practice  of  placing  flowering  branches  of 
plums  or  cherries  in  jars  of  water  and  hanging  them  in  a 

1  Hume,  H.  H.    Proc.  Soc.  Hort.  Sci.    1913.    pp.  88-93. 
-  Factors  influencing  the  ab.scission  of  flowers  and  partially  developed 
fruits  of  the  apple.    Proc.  Amer.  Soc.  Hort.  Sci.     1916. 


296  POMOLOGY 

tree  of  a  self-sterile  variety,  thus  affording  insects  an  op- 
portunity to  effect  cross-pollination. 

When  poUination  is  to  be  practiced  artificially,  for  exper- 
imental purposes  or  for  securing  new  varieties,  it  is  usual 
to  protect  the  essential  parts  of  the  flowers  in  order  to  assure 
accuracy.  The  blossoms  which  are  to  be  used  as  the  female 
parent  are  inclosed  prior  to  the  opening  of  the  petals.  The 
blossoms  from  which  the  pollen  is  to  be  secured  are  also  pro- 
tected in  order  to  prevent  a  mixture  with  foreign  pollen,  by 
insects,  or  other  agency.  This  covering  is  usually  a  paper 
bag,  either  manila  paper  or  a  translucent,  paraffined  bag  be- 
ing employed.  A  question  has  been  raised  occasionally  as  to 
whether  an  abnormal  condition  would  not  be  produced  in 
this  way  and  thus  reduce  the  possibilities  of  success.  How- 
ever, when  coverings  of  cheese-cloth  or  other  material  allow- 
ing a  passage  of  air  have  been  used,  no  increase  in  efficiency 
has  been  noted.  Others  have  covered  the  entire  areas  with 
a  frame  of  muslin  and  either  hand-pollinated  the  flowers  or, 
in  case  the  study  is  one  of  self-sterility,  bees  have  been  in- 
cluded. Such  an  equipment  has  some  advantages,  but  the 
percentage  of  set  is  not  greater  than  by  the  bag  method. 

In  manipulating  the  flowers,  it  is  customary  to  cover  the 
blossoms  just  before  they  are  ready  to  expand  and  expose 
the  essential  parts.  If  the  purpose  is  cross-fertilization,  the 
stamens  (and  often  petals)  are  removed  at  time  of  bagging, 
before  pollen  has  been  exposed,  so  that  danger  of  self-pollin- 
ation is  eliminated.  It  has  been  demonstrated  that  the  re- 
moval of  the  sepals  as  well  as  the  petals  and  stamens  has 
no  injurious  effect  in  securing  a  perfect  functioning  of  the 
pistils,  if  carefully  done.  When  the  work  is  performed  by 
a  novice  or  very  hurriedly,  it  is  doubtful  whether  this  proce- 
dure is  best,  since  fruits  may  be  deformed  by  careless  ma- 
nipulation and  many  stigmas  are  often  badly  injured.  The 
pollen  from  another  tree  is  frequently  collected  in  a  glass 


POLLINATION  AND  STERILITY  297 

vial  and  applied  with  a  camel's-hair  brush  or  the  finger. 
Others  pick  the  flowers  and  brush  the  anthers  over  the  pis- 
tils of  the  female  parent. 

THE    STERILITY    PROBLEM 

When  it  is  recognized  that  many  varieties  of  fruit  exhibit 
self-sterility,  inter-sterility,  and  self-barrenness,  and  hence 
require  cross-pollination  with  some  other  variety,  the  sub- 
ject becomes  one  of  great  economic  importance.  There  is 
considerable  variation  of  opinion  in  regard  to  the  ultimate 
causes  of  sterility,  and  consideration  here  can  well  be  con- 
fined to  some  of  the  established  facts  which  closely  pertain 
to   pomology. 

265.  Definition  of  terms. — Self-sterility  refers  to  the 
inability  of  a  plant  to  develop  fertile  seeds  when  the  pistil 
is  pollinated  with  pollen  from  its  own  flower  or  from  one  of 
the  same  variety  of  fruit.  Other  meanings  are  given  to  it, 
such  as  lack  of  development  of  any  fruit  at  all  when  the 
flower  is  self-pollinated.  It  must  be  understood  that  such  a 
condition  does  not  mean  that  either 'the  pistils  or  stamens 
are  defective  but  merely  that  fertilization  does  not  take 
place,  even  though  the  pollen  may  germinate  on  the  stigma, 
as  often  occurs;  or  if  fertilization  does  take  place,  the  young 
embiyo  does  not  complete  its  development.  The  ultimate 
reason  for  this  phenomenon  is  not  clear,  but  the  phrase 
"lack  of  affinity"  has  been  given  to  it.  In  other  cases,  the 
pollen  may  be  defective  and  hence  cause  self-sterility,  or 
the  embryo  sacs  may  be  defective. 

Self-fertility,  on  the  other  hand,  refers  to  the  ability  of  a 
plant  to  produce  genninable  seeds  when  its  pistils  are  pol- 
linated from  the  same  flower,  tree,  or  variety,  i.  e.,  in  the 
fertilization  of  the  ovule,  the  male  gametes  were  not  derived 
from  another  variety  or  species. 

Varieties  are  said  to  be  inter-sterile  when  certain  ones  fail 


298  POMOLOGY 

to  fertilize  one  another,  but  are  readily  fertilized  by  the  pol- 
len of  a  still  different  variety. 

These  various  phenomena  must  not  be  confused  with  the 
condition  that  exists  in  the  case  of  imperfect  flowers,  such 
as  with  some  of  the  strawberries.  Here  there  is  an  actual 
lack  of  one  of  the  essential  organs  (stamens).  The  term 
morphological  self-sterility  may  be  applied  to  this  case,  which 
is  not  infrequent  with  other  fruits  such  as  the  grape  and 
mulberry. 

It  has  been  shown  that  self-sterility  is  a  heritable  char- 
acter but  that  it  may  be  modified  by  changing  the  environ- 
ment. Fvn-ther,  a  tobacco  plant  which  is  ordinarily  self-sterile 
may  become  partially  fertile  and  produce  a  few  seeds  at  the 
end  of  a  flowering  period  and  under  conditions  adverse  to 
vegetative  growth .  ^ 

While  not  particularly  related  to  the  sterility  problem, 
the  term  parthenocarpy  may  here  be  defined.  This  indicates 
fruits  which  develop  wholly  independently  of  any  pollination 
of  the  stigmas  or  fertilization  of  the  ovules.  The  term  refers 
to  the  development  of  fruit  structures  other  than  the  seeds. 
This  phenomenon  is  not  uncommon  with  the  apple  and  pear.- 

Another  case  of  interest  and  quite  unlike  the  above  is 
when  the  flesh  of  the  fruit  develops  only  if  pollination  of  the 
stigmas  has  taken  place.  Fertilization  may  or  may  not  fol- 
low pollination,  but  if  so  there  is  an  abortion  of  the  embiyos 
at  a  more  or  less  advanced  stage  and  hence  no  viable  seeds 
develop. 

Thus,  finally,  all  fruit-trees  are  classed  as  either  barren  or 
fruitful,  and  if  the  former  they  are  always  sterile,  whereas 

lEast,  E.  M.,  and  J.  B.  Park.  Studies  on  self -sterility.  Genetics, 
2:505-609.    1917. 

2  See  Kraus,  E.  J.,  and  H.  R.  Kraybill.  Ore.  Agr.  Exp.  Sta.  Bull. 
149.  pp.  6-11.  Also  Sturtevant,  E.  Lewis.  Seedless  fruits.  Mem. 
Torrey  Bot.  Club,  Vol.  I,  No.  4,  1890. 


Plate  \'1I. — a.  Trees  grown  permanently  in  sod.  b.  Trees  grown 
under  the  grass  mulch  system,  c.  The  tillage-cover-crop  system 
used  in  this  orchard. 


POLLINATION  AND  STERILITY  299 

the  latter  may  be  sterile  or  fertile  depending  on  the  seed 
relationship. 

266.  Sterility  not  a  constant  factor. — Since  the  time  of 
Darwin  it  has  been  known  that  self-fertility  and  -sterility 
of  varieties  of  fruit  may  not  be  a  constant  characteristic, 
but  that  it  may  vary  with  the  age  of  the  trees,  health  and 
vigor,  climate,  general  ecological  conditions,  and  the  like. 
This  led  to  many  disputes  and  apparent  misstatements  until 
the  dual  behavior  of  a  variety  was  disclosed.  The  same  tree 
may  be  self-sterile  at  one  time  and  self-fertile  at  another. 
Vincent  ^  reviews  this  question  and  calls  attention  to  the 
case  of  the  Yellow  Newtown  apple  which  is  listed  as  self-ster- 
ile in  one  place  and  self-fertile  in  another,  while  the  same 
variation  is  recorded  for  the  Rhode  Island  Greening  and 
Grimes  Golden.  Garcia  reports  the  Bartlett  pear  as  self- 
fertile  in  New  Mexico  while  most  other  observers  record  it 
as  quite  self-sterile.  Gardner  ^  reports  a  similar  variation 
with  sweet  cherries  in  different  parts  of  Oregon. 

267.  Causes  of  sterility. — Kraus  ^  divides  the  causes  of 
sterility  into  two  general  groups:  (1)  morphological  and  (2) 
physiological.  Several  of  the  causes  belonging  to  the  first 
group  are  rather  well  known,  while  those  of  the  second  are 
more  complicated  and  intangible.  Among  the  more  im- 
portant of  the  former  may  be  listed  the  following:  (1)  a 
lack  of  germinability  of  pollen  which  in  some  cases  may 
amount  to  as  much  as  1  to  100  per  cent;  (2)  imperfect  pollen 
or  pollen  in  which  some  of  the  structures  have  degenerated; 
(3)  more  complete  abortive  pollen  as  occurs  with  some  of  the 
parthenocarpic  fruits;  (4)  imperfection  of  the  ovules  which 
is  frequent  in  many  kinds  of  fruit ;  (5)  a  physical  impossibil- 
ity of  self-fertilization  as  with  dioecious  plants;  (6)  various 

1  Better  Fruit,  Feb.,  1920. 

2  Ore.  Agr.  Exp.  Sta.  Bull.  116. 

^  The  self -sterility  problem.     Jour.  Heredity,  Dec.  1915. 


300  POMOLOGY 

modifications  of  perfect  flowers  which  prevent  self-pollina- 
tion; and  (7)  the  possible  case  of  the  inability  of  the  pollen- 
tube  to  grow  sufficiently  long  to  reach  the  ovaiy. 

Among  the  physiological  causes  the  following  may  be 
included:  (1)  possible  lack  of  nourishment  of  the  pollen- 
tube  in  the  case  of  some  pistils;  (2)  negative  chemotactic  ac- 
tion, although  this  is  not  known  to  occur  with  fruits;  (3)  pos- 
sible toxic  effect  of  the  stigmatic  fluid  on  the  pollen  or 
vice-versa  (investigations  tend  to  disprove  this  with  the 
fruits) ;  lack  of  fertilization;  lack  of  development  of  the  embryo 
after  fertilization  may  have  taken  place.  It  might  also  be 
added  that  hybridity  frequently  results  in  entire  sterility 
(heterosis).  In  studying  the  causes  of  self-sterility,  it  has 
been  observed  that  there  is  a  slow  growth  of  the  pollen- 
tube  which  results  in  a  lack  of  fertilization,  as  with  the  Rome 
Beauty  apple  ^  and  also  with  the  tobacco.-  In  the  latter 
case,  it  was  noted  that  the  pollen  germinates  as  freely  on 
the  stigmas  of  flowers  of  the  same  plant  as  those  of  other 
kinds  with  which  they  are  compatible.  After  germination, 
however,  the  pollen-tubes  on  selfed  flowers  grow  so  slowly 
that  decay  of  the  flower  occurs  before  fertilization  can  be 
effected. 

268.  The  cherry. — One  of  the  most  interesting  cases  of 
sterility  that  has  developed  in  American  pomology  is  that 
of  the  cheriy.  It  had  been  known  for  some  time  that  vari- 
eties of  the  sweet  cherry  in  particular  were  inclined  to  be 
self-sterile  and  were  not  parthenocarpic,  but  it  later  devel- 
oped not  only  that  the  sweet  cherry  was  practically  always 
self-sterile  as  grown  in  Oregon,  but  also  that  several  of  the 
standard  varieties  were  inter-sterile. 

This  appears  to  be  a  clear  case  of  "lack  of  affinity"  be- 
tween certain  varieties  and  is  not  due  to  any  lack  of  germin- 

iRnight,  L.  I.    Proc.  Amer.  Soc.  Hort.  Sci.    1917.     pp.  101-105. 
2  East,  E.  M.,  and  J.  B.  Park.     Genetics,  3:  353-366.    1918. 


POLLINATION  AND  STERILITY  301 

ability  of  the  pollen  or  to  defective  pistils,  as  was  demon- 
strated by  careful  tests. ^  The  three  varieties  notoriously 
inter-sterile  are  Bing,  Lambert,  and  Napoleon,  and  mixed 
plantings  of  them  will  give  little  or  no  fruit  unless  they  are 
within  the  range  of  influence  of  some  other  variety  that  is 
inter-fertilo  with  them.  Of  those  studied,  the  Black  Repub- 
lican, Black  Tartarian,  and  Waterhouse  seemed  to  be  the 
most  efficient  pollinizers  for  this  group. 

While  not  entirely  germane  to  the  sterility  problem,  it  is 
of  interest  to  note  that  some  members  of  the  Duke  group 
of  cherries  and  also  some  varieties  of  the  sour  cherries  (P. 
Cerasus)  are  capable  of  fertilizing  some  of  the  Bigarreaus. 
The  sour  cherries  are  usually  credited  with  being  self-fertile 
but  there  would  seem  to  be  many  exceptions  to  this  state- 
ment. 

269.  The  almond. — Tufts  ^  has  shown  that  all  the  com- 
mon varieties  of  almonds  grown  in  California  are  self-sterile 
to  a  large  extent  and  certain  of  them  are  inter-sterile.  The 
honey  bee  is  considered  the  best  pollinating  agent  for  the 
almond. 

270.  The  grape. — The  first  important  work  in  this 
countrj^  on  the  sterility  problem  of  the  grape  was  that  of 
Beach,  although  Goff  had  previously  shown  that  the  variety 
Concord  would  set  fruit  as  well  when  the  clusters  were  cov- 
ered with  a  bag  as  when  left  open.  Beach  found  that  "Cul- 
tivated American  grapes  show  remarkable  differences  in 
the  degree  of  self-sterility  of  different  varieties.  Many  of 
them  fruit  perfectly  of  themselves.  Others  form  no  fruit 
when  cross-pollination  with  other  varieties  is  prevented. 
Most  varieties  are  found  between  these  two  extremes,  being 
neither  fully  self-fertile  nor  completely  self-sterile."     After 

1  Gardner,  V.  R.    Ore.  Agr.  Exp.  Sta.  Bull.  116.    191.3. 
-  Tufts,  W.  F.    Almond  pollination.     Calif.  Agr.  Exp.  Sta.  Bull.  306. 
1919. 


302  POMOLOGY 

testing  169  cultivated  varieties  (and  many  seedlings),  he 
classified  them  as  follows: 

Class  I. — Self-fertile  varieties  having  perfect  clusters  or 
clusters  varying  from  perfect  to  somewhat  loose,  38  vari- 
eties (21.8%). 

Class  II. — Self -fertile  varieties  having  clusters  loose  but 
marketable,  66  varieties  (39.0%). 

Class  III. — Varieties  which  are  so  imperfectly  self-fertile 
that  the  self-fertilized  clusters  are  generally  too  loose  to  be 
marketable,  28  varieties  (16.5%). 

Class  IV.— Self-sterile  varieties,  37  varieties  (21.8%). 
He  also  noted  that  varieties  with  short  or  recurved  stamens 
are  always  self-sterile  or  nearly  so.  The  explanation  offered 
at  that  time  for  sterility  was  "a  lack  of  affinity  between  the 
pollen  and  pistils  of  the  same  variety."  ^ 

Dorsey  -  illustrates  the  method  of  testing  sterility  from 
the  work  of  Beach  as  follows: 

''When  143  clusters  of  Brighton  were  covered  with  bags 
and  self -pollinated,  the  average  rating  of  the  clusters  formed, 
counting  100  as  a  perfect  cluster,  was  approximately  one, 
and  when  thirty-two  clusters  distributed  among  eight  other 
varieties  were  pollinated  with  Brighton  pollen,  the  average 
rating  was  three,  showing  Brighton,  for  those  varieties  used, 
as  well  as  for  itself,  to  be  a  poor  poUenizer.  On  the  other 
hand,  when  116  clusters  of  the  Catawba  were  selfed,  the  av- 
erage rating  on  the  same  basis  as  above  was  eighty-six,  as 
compared  with  one  in  Brighton.  When  the  thirty-three 
clusters  of  eight  other  varieties  were  pollinated  with  pollen 
from  Catawba,  the  average  rating  was  sixty-seven,  showing 
a  marked  difference  between  the  Brighton  pollen  and  the 
Catawba  pollen  when  used  either  in  selfing  or  crossing." 

1  N.  Y.  Agr.  Exp.  Sta.  Bull.  157.     1898. 

2  Dorsey,  M.  J.  Jour.  Heredity,  6:  1915.  p.  243.  Minn.  Agr.  Exp. 
Sta.  Bull.  144.     1914. 


POLLINATION  AND  STERILITY  303 

It  has  been  shown  ^  that  a  marked  difference  in  appearance 
exists  between  the  dry  pollen  of  self-fertile  and  self-sterile 
grape  varieties.  The  former  or  normal  pollen  is  oblong  in 
outline  with  slightly  flattened  ends,  while  the  latter  is  quite 
irregular  and  folded,  and  fails  to  genninate  when  placed  in 
a  nutrient  solution. 

Dorsey  has  shown  that  the  development  of  the  pollen  in 
self-sterile  varieties  of  the  grape  is  normal  "up  to  the  forma- 
tion of  the  microspores,  but  here  a  degeneration  takes  place 
which  renders  the  pollen  grains  (microspores)  sterile."  A 
careful  study  of  the  pollen  produced  by  those  varieties  which 
bagging  tests  have  shown  to  be  more  or  less  self-sterile,  show 
that  the  generative  nucleus  and,  in  some  cases,  also  the  vege- 
tative nucleus,  degenerate.  Such  degeneration  precludes  the 
possibility  of  nomial  functioning  in  eveiy  pollen-grain  where 
it  occurs.  Sterile  pollen  in  the  grape,  then,  is  due  to  de- 
generation in  the  generative  nucleus. 

He  has  also  shown  that  "the  genn  spores  are  not  formed 
in  pollen  borne  by  the  reflexed  type  of  stamen." 

To  sunnnarize  the  causes  and  correlations  in  the  sterility 
of  the  grape,  the  following  statements  seem  warranted  from 
present  knowledge: 

1.  Self-sterility  in  the  grape  is  due  to  defective  pollen 
and  not  to  the  pistils. 

2.  "All  varieties  tested  set  fruit  when  potent  pollen  was 
used,  which  shows  that  the  pistils  are  normal." 

3.  Potent  pollen  can  be  distinguished  from  impotent  by 
its  shape  when  diy. 

4.  Impotent  pollen  is  correlated  with  the  reflexed  type 
of    stamens. 

5.  The  defective  pollen  is  due  to  an  abortion  of  the  gen- 
erative nucleus. 

These  studies  lead  to  one  veiy   practical   reconr.uenda- 
'  Booth,  N.  O.    N.  Y.  State  Agr.  Exp.  Sta.  Bull.  224,  291-302.    1902. 


304  POMOLOGY 

tion,  viz.,  mixed  plantings  of  the  grape  will  be  more  fruitful 
than  those  of  one  variety  only, 

271.  The  plum. — Some  of  the  most  extensive  investi- 
gations on  the  self-sterility  problem  have  been  with  the  plmn, 
notably  by  Bailey/  Waugh,-  Hendrickson,^  and  Dorsey.^ 
There  is  a  general  tendency  throughout  the  plum  species 
to  self-sterility  but  there  are  many  exceptions,  as  would  be 
anticipated  from  a  knowledge  of  the  problem.  The  salicina 
(Japanese)  varieties  are  as  a  rule  self-sterile  and  self-barren. 
The  Climax  is  the  only  one  of  several  kinds  observed  by 
Hendrickson  to  be  self-fertile  in  California.  He  also  reported 
that,  in  general,  the  early  blooming  Japanese  varieties  such 
as  Combination,  Kelsey,  and  Satsuma,  are  scanty  pollen- 
producers  and  not  effective  poUinizers,  while  the  later  blos- 
soming sorts  such  as  Burbank,  Wickson,  Climax,  Sultan,  and 
Abundance  produce  pollen  abundantly  and  are  effective 
pollinizers. 

Varieties  of  the  native  American  species  of  plums  vary- 
in  regard  to  the  sterility  character  but  are  much  inclined  to 
be  self-sterile,  as  is  notable  in  the  case  of  the  Wild  Goose 
which  is  perhaps  more  generally  grown  than  any  other  single 
kind.  They  are  for  the  most  part  fully  inter-fertile,  however, 
so  that  one  given  variety  will  pollinate  any  other,  providing 
the  two  bloom  at  the  same  time.''  Waugh  has  shown  that 
in  the  P.  americana  group  the  pistils  are  frequently  defec- 
tive, averaging  21.2  per  cent  in  the  trees  studies.  The  an- 
thers are  also  defective  in  some  cases  but  not  so  frequently 
as  the  pistils.    In  some  cases,  the  anthers  mature  before  the 

1  Bailey,  L.  H.    Cornell  Agr.  Exp.  Sta.  Bull.  52,  106,  139,  175. 

2  Waugh,  F.  A.     Vt.  Agr.  Exp.  Sta.  Ann.  Rept.     1897-98,  1898-99. 

3  Hendrickson,  A.  H.  Plum  pollination.  Calif.  Agr.  Exp.  Sta.  BuU. 
310.     1919. 

^  Dorsey,  E.  J.    Jour.  Agr.  Res.  17:  No.  3,  1919. 
^Waugh,  F.  A.    Standard  Cycl.  Hort.  V:  2719.     (1916.) 


POLLINATION  AND  STERILITY  305 

pistils  are  receptive  (proterandrous),  while  in  other  cases 
the  pistils  mature  before  the  pollen  is  ripe  for  pollination 
(proterogynous). 

It  is  true,  however,  as  has  been  stated,  that  the  Japan- 
ese and  American  plums  are  generally  inter-fertile  both 
within  their  respective  species  and  also  in  hybridizing  be- 
tween the  species.  P.  americana  is  less  inclined  to  hybridize 
than  some  other  species  of  American  plums. 

The  Domestica  plums  (European  species)  are  variable, 
some  varieties  being  self-fertile  and  others  self-sterile,^  but 
as  a  class  they  may  be  considered  inter-fruitful.-  They  are, 
however,  largely  inter-sfcerile  with  Japanese  and  American 
plums  but  may  be  inter-fertile  to  some  degree,  as  indicated 
by   Hendrickson.^ 

He  has  shown  also  that  the  French  prune  is  abundantly 
self-fertile  in  California  if  bees  are  present  to  work  over 
the  blossoms,  but  that  the  Imperial  prune  is  very  much 
less  so.  His  work  with  these  varieties  well  illustrates  the 
value  of  the  common  honey  bee  as  an  agent  in  prune  pollin- 
ation.^ The  following  data  which  he  obtained  are  self- 
explanatoiy: 

1  Bailey,  L.  H.    Principles  of  Fruit-Growing,  20th  Ed.    p.  158.     1915. 

2  Marshall,  Roy  E.    Proc.  Amer.  Soc.  Hort.  Sci.     1919.    p.  42. 

3  Hendrickson,  A.  H.    Proc.  Amer.  Soc.  Hort.  Sci.    1919.    p.  50. 

*  As  an  interesting  side  light  on  the  application  of  these  pollination 
studies,  the  following  excerpt  is  quoted  from  W.  L.  Howard,  letter, 
dated  March  11,  1920.  "Our  investigations  in  the  Santa  Clara  Valley, 
zarried  on  for  five  years,  showed  that  bees  are  an  important  factor  in 
prune  pollination.  Before  our  investigations  were  started,  bee  men  paid 
the  fruit  growers  from  50c  to  .$1.00  an  acre  for  the  privilege  of  pasturing 
their  bees  in  the  orchards  during  the  blooming  season.  Since  our  ex- 
perimental findings  were  published,  three  years  ago,  there  has  been  a 
complete  change  in  the  situation.  This  sea.son  bee  men  have  been  able 
to  rent  every  hive  they  have  to  fruit  growers  for  from  S2.00  to  $3.00 
per  hive,  depending  upon  whether  they  are  bunched  in  one  place  or 
scattered  over  the  orchard." 


306 

POMOLOGY 

Table  LXXXVI 

BEHAVIOR  OF  FRENCH  PRUNE  TREES  WITH  AND  WITHOUT 

CROSS-POLLINATION       (AFTER  HENDRICKSON) 

1916 

1917 

Per  cent 

Per  cent 

3.5 

13.2 

Set  on  trees  from  which  bees 

were  excluded 

1.04 

0.43 

FRENCH  PRUNE 

Set  on  trees  inclosed  with  bees 
and  with  an  Imperial  prune 

tree 

18,05 

15.5 

Set  on  tree  inclosed  with  bees 

19.4 

Average  orchard  set 

7.2 

7.2 

Set  on  trees  from  which  bees 

were  excluded 

0.0 

0.34 

IMPERIAL  PRUNE 

Set  on  trees  inclosed  with  bees 

and  with  French  prune 

1.7 

7.9 

Set  on  trees  inclosed  with  bees 

alone                             

3.02 

In  many  cas3s  of  experimentation,  plums  have  been  more 
highly  inter-fruitful  than  inter-fertile,  some  producing  fruits 
which  contained  abortive  seeds. 

272.  The  peach. — Unhke  practically  all  other  fruits, 
the  peach,  as  a  rule,  is  quite  self-fertile  and  capable  of  set- 
ting and  maturing  a  crop  when  self-  or  close-pollinated. 

Fletcher  reports,  "The  results  of  hand-pollinating  2939 
Gold  Drop  peach  blossoms  in  1906  showed  no  benefit  to  this 
variety  from  cross-pollination  with  St.  Johns,  Late  Cran- 
ford,  or  Lewis;  the  self-fertilized  fruits  were  perhaps  a  trifle 
superior."  All  experiments  confirm  this  work  in  general 
and  the  recommendation  that  peaches  of  one  variety  may 
be  planted  in  a  solid  block  is  standard,  although  growers 
frequently  feel  that  they  prefer  to  mix  them  somewhat. 


POLLINATION  AND  STERILITY  307 

273.  The  quince  is  reported  by  Waite  to  be  nearly  as 
fruitful  when  self-pollinated  as  when  cross-pollinated. 

274.  The  apple. — As  a  class,  the  apple  is  inclined  to  be 
self-sterile  although  a  number  of  varieties  are  known  to  be 
at  least  partially  self -fertile.  In  contrast  with  the  grape,  the 
sterility  is,  according  to  Kraus,  "due  almost  wholly  to  em- 
bryo abortion,"  and  Knight  ^  says  also  to  lack  of  pollen- 
tube  growth.  From  a  practical  standpoint,  it  is  always  bet- 
ter to  have  mixed  plantings  than  a  solid  block  of  one  variety, 
although  the  latter  may  be  successful  under  some  conditions. 

Waugh  worked  with  eighteen  varieties  of  apple  commonly 
grown  in  New  England  and  reported  them  all  to  be  practi- 
cally self-sterile.  Out  of  258(3  blossoms  covered,  only  three 
apples  set,  or  l/lO  of  1  per  cent. 

Lewis  and  Vincent  reported  that  of  eighty-seven  varieties 
tested,  fifty-nine  were  self-sterile,  fifteen  self-fertile,  and  thir- 
teen partially  self-fertile." 

Waite  states  that  "The  varieties  of  apples  are  more  in- 
clined to  be  sterile  to  their  own  pollen  than  the  pears.  With 
the  former,  in  the  great  majority  of  cases,  no  fruit  resulted 
from  self-pollination." 

Alderman  ^  investigated  the  Rome  Beauty,  York  Impe- 
rial, and  Wagener  for  a  period  of  three  years,  with  the  follow- 
ing results: 

iProc.  Soc.  Hort.  Sci.     1917. 

2  Ore.  Agr.  Exp.  Sta.  Bull.  104.     1909. 

3  Loc.  cit. 


308 


POMOLOGY 


Table  LXXXVII 

effect  of  cross-pollination  on  the  set  of  fruit 

(after  alderman) 


Number 

Fruits 

Per  cent 

blooms 

set 

set 

16,826 

168 

.99 

20,587 

702 

3.41 

21,742 

129 

.59 

25,775 

2,137 

8.29 

3,407 

43 

1.26 

6,993 

611 

8.73 

Rome  Beauty,  not  crossed . 

Rome  Beauty,  crossed 

York  Imperial,  not  crossed 
York  Imperial,  crossed .  .  .  . 

Wagener,  not  crossed 

Wagener,  crossed 


Here  it  will  be  seen  that  the  set  of  fruit  was  materially 
increased  by  crossing.  The  percentage  of  set  was  increased 
with  the  Rome  three  and  a  half  times,  with  the  York  four- 
teen, and  with  the  Wagener  seven  times.  In  addition,  the 
weight  of  the  Rome  was  increased  nearly  28  per  cent  and  the 
York  42.7  per  cent  over  the  size  of  the  self-pollinated  fruits. 

275.  The  pear. — Since  many  varieties  of  pears  are  self- 
sterile  and  probably  because  of  the  influence  of  the  work  of 
Waite,^  considerable  attention  has  been  given  to  a  study  of 
this  fruit.  Bailey  ^  says  "Many  of  the  varieties  of  pears  are 
infertile  with  themselves:  they  need  the  pollen  of  other  va- 
rieties to  cause  them  to  set  fruit  freely.  Probably  any  va- 
riety will  fertilize  any  other  variety  in  case  the  two  bloom 
simultaneously."  Waite  showed  that  out  of  thirty-six  va- 
rieties tested,  twenty-two  were  self-sterile,  but  called  partic- 
ular attention  to  the  sterility  of  the  Kieffer. 

Fletcher  ^  has  shown  that  "unsatisfactory  results  may  be 
expected  from  planting  either  Bartlett  or  Kieffer  in  large 
blocks,  so  that  cross-pollination  by  insects  is  not  general. 

'  Loc.  cit. 

2  Standard  Cycl.  Hort.  V:  2506. 

3  Va.  Agr.  Exp.  Sta.  Ann.  Rept.    1909-10.    pp.  213-224. 


POLLINATION  AND  STERILITY 


309 


Anjou,  Lawrence,  Duchess,  and  Kieffer  are  satisfactoiy  va- 
rieties for  planting  with  Bartlett  so  far  as  pollination  is  con- 
cerned. Some  years  Kieffer  does  not  blossom  simultaneously 
with  Bartlett,  but  usually  the  blossoms  overlap  sufficiently. 
Le  Conte,  Garber,  Lawrence,  Bartlett,  Duchess,  Anjou,  and 
Clairgeau  are  satisfactoiy  varieties  for  planting  with  Kief- 
fer, so  far  as  pollination  is  concerned.  Some  seasons  the 
latter  five  varieties  do  not  blossom  simultaneously  with 
Kieffer,  but  usually  the  blossoming  seasons  overlap  suffi- 
ciently." 

He  obtained  the  following   results  under  Virginia  condi- 
tions: 

Table  LXXXVIII 


RESULTS    OF    SELF-    AND    CROSS-POLLINATION    OF    BARTLETT    PEAR 
(aTER  FLETCHER) 

PoUi7iations 

Average  amount  of 
blossoms  set 

Average  weight  of 

mature  fruit, 

ounces 

Bartlett  X  Bartlett 

"       X  Kieffer 

"       X  Anjou 

1  in  513 
1  in  10 
1  in  7 
1  in  9 
1  in  10 

2.00 
3.00 
3.75 
3.50 

"       X  Angoulerae  (Duchess) 

3.50 

In  Califoniia  the  Bartlett  is  grown  very  extensively  and, 
in  spite  of  the  advice  given  to  the  growers  to  inter-plant 
with  other  varieties,  there  are  large  blocks  planted  alone. 
As  a  result  of  this  situation,  some  experiments  were  con- 
ducted during  1916-18  by  Tufts  ^  to  determine  the  status 
of  the  sterility  (barrenness)  of  this  variety  in  California  and 
to  detennine  the  best  poUinizers,  if  such  are  necessary. 

It  was  found  that  the  Bartlett  is  to  a  limited  degree  self- 
sterile  under  valley  conditions,  but  entirely  so  in  the  foot- 
*  Tufts,  H.  P.    Calif.  Agr.  Exp.  Sta.  BuU.  307.    1919. 


310  POMOLOGY 

hills.  Hence  it  is  advisable  to  inter-plant  with  one  or  more 
varieties  for  cross-pollination  purposes.  These  experiments 
showed  that  the  Angouleme,  Anjou,  Clairgeau,  Cornice, 
Dana  Hovey,  Easter,  Howell,  and  Winter  Nelis  will  all  pol- 
linate the  Bartlett  successfully. 

It  was  also  learned  that  no  cases  of  inter-sterility  existed 
between  the  varieties  studied  and,  therefore,  any  which 
blooms  with  the  Bartlett  will  be  a  suitable  pollinizer.  Also, 
there  does  not  appear  to  l^e  the  same  tendency  to  fall  at  the 
June  drop  if  cross-pollination  has  taken  place. 


CHAPTER  XIII 

THE  ORIGIN  AND  IMPROVEMENT  OF  FRUIT 

In  a  study  of  the  vast  number  of  fruit  varieties  now  grown 
in  America,  the  fortuitous  nature  of  their  origin  is  impres- 
sive. The  larger  part  of  the  varieties  of  apples  planted  in 
this  country  originated  here,  but  the  histoiy  of  many  is  ob- 
scure and  only  a  veiy  few  came  into  existence  as  the  result 
of  direct  breeding.  This  statement  is  true  in  large  part  for 
the  other  fruits  also,  in  contrast  to  such  other  horticultural 
crops  as  flowers,  ornamentals,  and  vegetables.  Some  work- 
ers have  devoted  their  hves  to  the  production  of  new  fruits, 
but  not  until  comparatively  recent  times  have  practical  re- 
sults of  much  consequence  been  secured  through  breeding. 

The  histoiy  of  the  activities  of  man  in  the  origin  and  es- 
tablishment of  American  pomology  is  highly  interesting, 
much  of  it  being  available  in  the  writings  of  Bailey. 

The  outstanding  difficulties  in  the  production  of  new  fruits 
by  breeding  or  in  the  study  of  the  laws  of  inheritance  as  they 
pertain  to  fruit-trees  are:  (a)  the  length  of  time  required  to 
secure  the  fruit  of  a  new  generation;  (b)  the  small  number 
of  individuals  that  can  be  handled  in  such  work  with  the 
larger  tree-fruits;  and  (c)  self-sterility,  which  is  often  en- 
countered in  lines  of  attack. 

The  first  great  stimulus  to  the  breeding  of  fruits  came 
from  the  conspicuous  work  of  Van  Mons  in  Belgium  and 
Knight  in  England.  The  theories  and  work  of  these  men 
should  be  perpetuated  in  our  literature. 

276.  Theory  of  Van  Mons. — Jean  Baptiste  Van  Mons  was 
a  celebrated  chemist  of  Belgium  (1765-1842)  who  became 
311 


312  POMOLOGY 

interested  in  the  improvement  of  fruits,  particularly  the 
pear.  He  placed  himself  in  the  unfortunate  position  of 
conceiving  a  theoiy  and  setting  about  to  prove  it.  How- 
ever, in  so  doing,  he  greatly  stimulated  the  science  of  plant- 
breeding;  and  although  his  theory  was  without  foundation, 
the  net  result  of  his  work  is  a  landmark  in  the  progress  of 
the  origination  of  new  varieties  of  fruits. 

His  theory,  in  brief,  may  be  summarized  as  follows:^  All 
fine  fruits  are  artificial  products;  the  aim  of  nature,  in  a  wild 
state,  being  only  a  healthy  vigorous  tree,  and  perfect  seeds 
for  continuing  the  species.  It  is  the  object  of  cultivation, 
therefore,  to  subdue  or  enfeeble  this  excess  of  vegetation; 
to  lessen  the  coarseness  of  the  tree;  to  diminish  the  size  of 
the  seeds;  and  to  refine  the  quality  and  increase  the  size  of 
the  flesh  or  pulp. 

There  is  a  tendency  for  fruit-trees  to  return,  by  means  of 
their  seed,  to  a  wild  state,  and  such  a  tendency  is  more 
marked  in  old  trees  than  in  young  ones.  Hence,  the  older  a 
tree  is  the  nearer  will  the  seedlings  raised  from  it  approach 
a  wild  state,  although  they  will  never  return  entirely  to  it. 
Therefore,  in  order  to  secure  superior  varieties,  the  seed 
from  young  trees  only  should  be  selected,  as  these  are  in  a 
state  of  amelioration.  Again,  there  is  a  certain  limit  to 
perfection  in  fruits.  When  this  point  is  reached,  as  in  the 
finest  varieties,  the  next  generation  will  be  more  likely  to 
produce  poor  fruit,  than  that  from  seeds  of  an  indifferent 
sort  in  the  course  of  amelioration. 

In  following  out  this  theory,  Van  Mons  began  with  seeds 
from  inferior  sorts  and  sowed  a  new  generation  as  soon  as 
fruit  could  be  procured  from  the  last  sown,  continuing  this 
process  year  after  year.    "To  sow,  to  re-sow,  to  sow  again, 

1  Van  Mons,  J.  B.  Arbres  Fruitiers.  1835-36.  Downing,  A.  J. 
Fruits  and  Fruit  Trees  of  America.  1900.  pp.  5-7.  Bailey,  L.  H. 
The  Survival  of  the  Unlike,    pp.  141-151.    1897. 


ORIGIN  AND  IMPROVEMENT  OF  FRUIT         313 

to  sow  perpetually;  in  short  to  do  nothing  but  sow  is  the 
practice  to  be  pursued  and  which  cannot  be  departed  from." 

He  concluded  that  pears  require  the  longest  time  to  attain 
perfection,  and  he  cari'ied  the  process  with  this  fruit  through 
five  generations.  Apples,  he  found,  needed  but  four  races, 
and  peaches,  cherries,  plums,  and  other  stone-fruits  were 
brought  to  perfection  in  three  successive  reproductions  from 
the  seed. 

''Van  Mons'  work,  which  was  largely  confined  to  pears, 
was  begun  in  1785.  Thirty  years  later,  in  1823,  when  he  had 
commenced  distributing  scions  freely  throughout  the  world, 
he  had  80,000  seedling  trees  in  his  nursery.  At  this  time  his 
first  catalog  was  issued  and  in  it  1050  pears  were  mentioned 
by  name  or  number.  Of  this  list  405  were  his  own  creation 
and  200  of  them  had  been  considered  worthy  of  naming, 
among  them  being  some  of  the  varieties  still  raised  the  world 
over,  including  Diel,  Bosc,  Colmar,  Manning's  Elizabeth, 
and  many  others  of  equal  merit. 

"Probably  no  worker  with  plants  has  ever  given  to  the 
world  so  clear  a  demonstration  of  the  value  of  selection  as 
Van  Mons;  and  this  demonstration  is  worth  all  the  efforts 
put  forth,  even  though  this  was  made  in  the  attempt  to 
prove  another  and,  as  is  now  believed,  erroneous  doctrine."  ^ 

277.  Work  of  Knight.— Thomas  Andrew  Knight  (1759- 
1838)  was  the  first  practical  and  scientific  breeder  of  fruits. 
Bailey  describes  him  as  a  man  "who  in  the  variety,  accuracy, 
significance  and  candor  of  his  experiments  stands  to  the 
present  day  without  a  rival  amongst  horticulturists."  He 
conducted  experiments  which  are  still  standard  in  plant 
physiology  and  horticulture. 

Knight  avoided  the  error  of  Van  Mons,  that  of  having  a 
theory  to  prove,  but  devoted  himself  to  a  study  of  nature 

•  Munson,  M.  W.  Plant  breeding  in  its  relation  to  American 
pomology.    Maine  Agr.  Exp.  Sta.  Bull.  132.    1906. 


314  POMOLOGY 

and  to  the  results  of  his  manipulation  of  plants.  Van  Mons 
worked  entirely  along  the  line  of  selection  of  the  best  from 
each  generation,  but  Knight  was  the  first  actually  to  cross- 
breed fruits  in  order  to  secure  better  varieties.  That  his 
conception  of  the  problem  was  different  from  that  of  Van 
Mons  and  far  in  advance  of  it  is  shown  from  the  following 
statement  (1806) :  "New  varieties  of  species  of  fruit  will  gen- 
erally be  better  obtained  by  introducing  the  farina  of  one 
variety  of  fruit  into  the  blossoms  of  another,  than  by  prop- 
agating any  from  a  single  kind."  His  investigations  in- 
cluded apples,  pears,  plums,  peaches,  nectarines,  cherries, 
and  strawberries,  and  he  produced  several  varieties  of  each 
which  were  standard  in  their  day.  Hence  to  this  early 
worker  is  owed  the  beginning  of  real  progress  in  the  improve- 
ment of  fruits  and  the  methods  to  be  employed  in  securing 
them.  Knight  spent  considerable  time  in  studying  the  dura- 
tion of  varieties  of  fruit.  This  work,  while  not  entirely  ger- 
mane to  the  present  subject,  is  worth  recording,  although 
it  is  not  now  accepted.  His  theory  may  be  briefly  smnmarized 
as  follows: 

The  life  of  a  variety  of  fruit  is  about  as  long  as  the  life  of 
the  original  tree  which  produced  it;  cions  or  buds  taken  from 
the  tree  will  not  come  into  bearing  until  the  original  tree 
bears  fruit;  and  all  trees  propagated  from  the  parent  will 
die  soon  after  the  death  of  the  original  tree.  Or,  in  other 
words,  the  life  of  a  variety  is  about  as  long  as  the  natural 
life  of  the  tree  which  produced  it. 

This,  then,  is  a  brief  statement  of  two  of  the  most  inter- 
esting personalities  in  horticulture.  It  will  be  instructive 
to  contrast  their  views  with  some  of  the  more  modem  theories 
in  the  breeding  of  horticultural  plants. 

278.  Selection  as  a  means  of  securing  new  fruits. — 
The  voluntary  act  of  selection  must  enter  into  every  method 
of  securing  new  or  improved  varieties  of  fruits.    It  refers  to 


ORIGIN  AND  IMPROVEMENT  OF  FRUIT        315 

the  individual  choosing  of  forms  that  meet  the  ideal  of  the 
person  conducting  the  work  and  has  been  unconsciously  prac- 
ticed by  man  in  all  stages  of  civilization  since  the  time  he 
began  to  cultivate  plants  and  to  domesticate  animals.  With 
plants  commonly  grown  from  seed,  such  as  grains  and  vege- 
tables, this  method  of  improvement  has  found  wide  usage 
and  has  been  claimed  by  some  to  be  the  only  means  neces- 
sary. This  belief  is  founded  on  the  principle  of  variation, 
and  on  the  fact  that  all  possible  genetic  combinations  may 
occur  in  natural  crosses.  With  fruit-trees,  however,  selection 
as  a  method  of  plant  improvement  has  been  given  less  at- 
tention, as  fruits  are  reproduced  asexually.  Every  Baldwin 
apple  or  Elberta  peach  tree  is  a  part  of  the  original  tree 
which  was  a  chance  seedling. 

Such  being  the  case,  there  remain  but  two  methods  of 
selection  with  fruits:  namely,  of  bud  sports  or  mutations, 
and  of  new  forms  that  have  come  from  seed.  The  latter 
may  properly  be  subdivided  into  three  phases:  (1)  a  choice 
of  trees  that  are  chance  seedlings,  in  the  origin  of  which 
man  has  played  no  part;  (2)  a  selection  of  the  superior  trees 
from  a  miscellaneous  lot  of  seeds  sown;  and  (3)  a  selection 
of  trees  which  result  from  flowers  crossed  or  hybridized  by 
the  grower. 

First,  it  must  be  recognized  that  man  has  nothing  what- 
ever to  do  with  the  occurrence  of  the  superior  individual  or 
variety  under  the  first  two  methods  of  selection,  but  rather 
he  "finds"  it.  On  the  other  hand,  through  crossing  or 
hybridizing,  new  forms  may  be  secured  by  the  combination 
of  desirable  characters  within  one  plant,  or  by  "breaking  the 
type"  or  causing  the  original  plant  to  vary. 

The  chief  methods  of  selection  commonly  used  in  im- 
proving plants  are:  (1)  mass;  (2)  line;  and  (3)  clonal  selec- 
tion. The  method  will  of  necessity  depend  on  the  object  in 
view  and  the  nature  of  the  material  used  in  breeding. 


316  POMOLOGY 

The  terms  "mass  selection"  and  "line  selection"  cannot 
properly  be  applied  to  the  methods  employed  in  obtaining 
new  fruits.  They  refer  to  securing  an  improved  variety  in 
plants  that  are  propagated  sexually  (i.  e.,  by  seed),  where 
an  effort  is  made  in  each  generation  to  obtain  individuals 
that  will  be  superior  to  the  original  form, 

279.  Mass-selection  refers  to  the  choice  of  several 
superior  individuals  from  which  seed  would  be  sown  en  masse, 
no  effort  being  made  to  keep  the  progeny  from  any  single 
plant  separate;  and  from  the  new  individuals  which  arise, 
the  superior  ones  would  again  be  selected,  until  a  strain  or 
race  is  secured  which  is  superior  to  the  original  stock.  Such 
a  process  has  never  been  undertaken  with  fruit-trees,  since 
it  is  not  necessary  for  a  variety  to  be  homozygous  in  order 
to  propagate  it  asexually  or  for  it  to  have  superior  fruit 
characteristics. 

The  term  mass-selection  may  be  applied  in  a  broad  way 
to  the  method  used  by  Van  Mons  and  to  that  of  Burbank. 
Seeds  selected  from  one  or  more  trees  (themselves  heterozy- 
gous) are  planted  in  order  to  secure  a  large  number  of  new 
individuals.  From  these  new  forms  the  superior  ones  are 
selected,  usually  after  they  come  into  fruiting,  and  are  prop- 
agated as  new  varieties  with  no  further  selection. 

280.  Line-selection  has  no  special  application  to  fruits 
because,  as  yet,  no  one  has  tried  to  secure  a  race  or  variety 
which  will  come  true  from  seed,  as  is  necessary  with  the 
common  farm  and  garden  crops.  With  the  latter  plants,  the 
term  refers  to  a  line  of  progeny  derived  originally  from  one 
individual. 

281.  Clonal-selection. — The  term  "  clonal-selection  "  ap- 
plies only  to  plants  which  are  propagated  asexually,  hence 
to  fruit-trees.  Clones  have  been  defined  as  "groups  of  culti- 
vated plants  the  different  individuals  of  which  are  simply 
transplanted  parts  of  the  same  individual,  the  reproduction 


ORIGIN  AND  IMPROVEMENT  OF  FRUIT        317 

being  by  the  use  of  vegetative  parts  such  as  bulbs,  tubers, 
buds,  grafts,  cuttings,  runners,  and  the  hke.  The  various 
sorts  of  apples,  .  .  .  commonly  denominated  varieties  in  a 
more  restricted  sense  would  be  clons.  Clons  of  apples,  pears, 
strawberries,  and  the  like,  do  not  propagate  true  to  seed, 
while  this  is  one  of  the  most  importaat  characters  of  races 
and  strains  of  wheat,  corn  and  others."    (Webber.) 

Hence,  any  selection  for  propagation  of  superior  trees  of 
any  of  the  fruits  would  properly  be  termed  "clonal-selection." 
Thus,  a  tree  which  appears  different  from  others  in  a  planta- 
tion or  is  superior  to  them,  as  being  a  regular  or  heavj^  bearer, 
having  better  color,  quality,  or  size  of  fruit,  or  being  particu- 
larly hardy ,  might  be  selected  for  the  purpose  of  propagating 
a  desirable  variation  within  the  clone.  The  temi  "strain" 
is  commonly  used  in  referring  to  such  differences.^ 

282.  Bud-selection,  as  commonly  used  in  horticultural 
literature,  refers  to  the  selection  of  a  bud  or  branch  which 
shows  a  superiority  over  or  difference  from  the  remainder  of 
the  tree.  Instead  of  the  whole  tree  being  the  unit  of  variation, 
the  individual  bud  is  the  unit  atid  is  so  selected.  Before  dis- 
cussing the  improvement  of  fruits  by  clonal-  or  bud-selection, 
it  should  be  determined  whether  such  variations  occur 
within  the  tree-fruits.  The  data  refer  to  deciduous  fruit- 
trees  for  the  most  part,  although  the  bud  variations  which 
have  been  reported  for  citrus  fruits  are  so  conspicuous  that 
they  are  mentioned  in  this  connection. 

283.  Individuality  of  fruit-trees. — It  is  well  known  that 
many  plants  have  given  rise  to  bud-sports  or  mutations, 
particularly  under  high  cultivation,  such  as  greenhouse  roses 
and  carnations.  Here  such  variations  as  the  occurrence  of 
a  pink  rose  on  a  plant  producing  white  ones  or  a  change  in 
form  of  the  flower  have  been  so  distinct  as  to  be  unmistak- 

^  Babcock  and  Clausen.  Genetics  in  Relation  to  Agriculture. 
McGraw-Hill  Co.,  New  York.     1916. 


318 


POMOLOGY 


able.  With  fruit-trees  it  has  been  more  difficult  to  determine 
between  variations  due  to  environment  and  not  of  a  per- 
manent character  and  those  which  are  true  bud-sports. 

The  following  data  are  presented  to  show  that  decided  va- 
riations do  occur  between  fruit-trees  of  the  same  variety 
(clones)  and  between  branches  of  the  same  tree,  but  whether 
they  are  due  to  internal  or  external  causes  is  not  determined. 
It  is  assumed  that  the  trees  are  always  comparable  and  that 
there  is  no  apparent  external  cause  for  the  variation. 


Table  LXXXIX 

the  variations  in  yield  of  bearing  apple  trees  as  reported  by 

several  experimental  stations  in  america 


New  York  ' 

exp. 

Trees, 
sta.  numbers 

Total  yield  for  10  years, 
bushels 

Ratio 

2  and  6 

246.5 
137.2 

179  6 

1  and  4 

100.0 

Canada  ' 

Tolal  yield  for  14  years, 
gallons 

4  trees 

477.94 
165.50 

288  0 

4  trees 

100.0 

Maine  ^ 

Total  yield  for  5  years, 
barrels 

10  trees 

157.9 
38  0 

415.5 

10  trees 

100  0 

Stewart,  J.  P.    Penn.  Agr.  Exp.  Sta.  Ann.  Rapt.     1911. 


ORIGIN  AND  IMPROVEMENT  OF  FRUIT        319 


Table  LXXXIX— Con/inue(Z 
New  Hampshire  ^ 


Tree 

Total  yield  for  6 
poimds 

years, 

No.  3 

4432 
1527 
515 

860 

269 

No.  15 

100 

No.  278 

Group  D     No.  280 

4204 

6817 

591 

711 
1153 

No.  281 

100 

It  will  be  seen  from  this  table  that  there  are  conspicuous 
differences  in  yield  of  seperate  trees  or  sets  of  trees  in  the 
same  orchard.  The  time  covered  by  these  records  is  sufficient 
to  eliminate  short-time  differences.  Such  variations  in  yield 
have  an  important  economic  bearing  and  some  of  the  out- 
standing instances  of  attempts  to  improve  fruits  by  bud- 
selection  may  be  noted. 

284.  Results  of  selecting  bud  variations. — If  the  data 
are  granted  to  prove  that  decided  variations  occur  between 
trees  and  their  branches  and  that  they  are  consistent  year 
after  year,  then  the  question  arises  as  to  whether  such  varia- 
tions are  permanent  in  nature  (mutants)  or  whether  they  are 
due  to  some  undetermined  local  condition  (fluctuating  varia- 
tions) and  hence  are  not  transmissible  by  asexual  propaga- 
tion. Unfortunately,  sufficient  work  has  not  yet  been  done 
to  establish  this  point  definitely,  but  most  of  the  evidence 
for  deciduous  fruit-trees  warrants  the  conclusion  that  such 
variations  cannot  usually  be  propagated  (asexually)  and 
hence  the  burden  of  proof  lies  with  those  who  make  such 

1  Gourley,  J.  H.  N.  H.  Agr.  Exp.  Sta.  Tech.  BuU.  9.  1915.  See  also 
Gardner,  V.  R.  Bud  selection  with  special  reference  to  the  apple  and 
strawberry.     Mo.  Agr.  Exp.  Sta.  Res.  Bull.  39.     1920. 


320  POMOLOGY 

claims.  There  are  a  few  cases,  however,  which  indicate  the 
origin  of  new  varieties  in  this  way,  although  for  the  most 
part  they  represent  an  increase  or  change  in  color,  as  varia- 
tion of  other  characteristics  is  not  common. 

Among  apples,  the  Banks  is  recorded  as  a  bud-sport  of  the 
Gravenstein,  differing  from  the  latter  in  being  more  highly 
colored,  less  ribbed,  more  regular  in  shape,  and  a  little 
smaller  in  size.  Other  sports  of  the  Gravenstein  have  been 
reported  in  Europe  and  in  this  country.  Two  bud-sports  are 
credited  to  the  Twenty  Ounce  apple — Collamer  and  Hitch- 
ings.  The  former  bears  fruits  less  mottled  and  striped,  more 
highly  colored  and  more  regular  in  shape.  The  twigs  of 
Collamer  trees  are  more  deeply  tinged  with  red  than  are 
those  of  Twenty  Ounce.  Hitchings  also  produces  more 
highly  colored  fruit  than  its  parent.  The  same  sort  of  muta- 
tion has  been  recorded  in  several  places  for  Rome  Beauty, 
the  fruit  of  the  new  forms  being  a  solid  dark  red,  smaller, 
and  quite  regular  in  size. 

Red  Russet  is  another  bud-sport  which  originated  in  New 
Hampshire  as  a  variation  of  Baldwin.  This  is  the  only  au- 
thentic variation  of  the  Baldwin  which  has  been  propagated, 
although  it  varies  widely  in  different  localities. 

Dorsey  ^  describes  an  "improved  Duchess"  apple  which 
seems  to  be  a  bud  mutation,  although  conclusive  evidence 
cannot  be  produced.  The  new  form  is  identical  with  the  old 
in  all  characters  except  color,  which  is  much  brighter  and 
redder.  Trees  propagated  from  the  red  type  retain  the 
character,  and  this  seems  to  add  another  to  the  list  of  fruits 
originating  as  bud  mutations. 

Another  interesting  case  of  a  bud-sport  or  mutation  de- 
scribed by  Shamel  ^  is  an  improved  French  prune.     This 

iDorsey,  M.  J.    Jour.  Heredity,  Dec,     1917.    p.  565. 
2  Shamel,  A.   D.     Origin  of    a  new   and   improved    French   prune 
variety.    Jour.  Heredity,  Nov.,  1919.    pp.  339-343. 


ORIGIN  AND  IMPROVEMENT  OF  FRUIT        321 

variety  is  grown  more  largely  in  California  than  any  other, 
but  the  small  size  has  been  a  matter  of  concern,  and  many 
efforts  have  been  made  to  improve  it.  Leonard  Coates,  a 
nurseryman  and  fruit-grower  of  Morganhill,  California,  ob- 
served a  branch  of  a  French  prune  tree  that  produced  fruit 
of  large  size.  Grafts  of  it  were  inserted  into  peach  stock 
and  the  new  form  was  found  to  be  identical  with  that  of 
the  original  branch.  Extensive  tests  were  made  to  deter- 
mine its  value,  and  so  successful  do  they  appear  that  it  is 
believed  it  may  prove  to  be  "the  most  valuable  addition 
to  the  commercial  prune  varieties  ever  introduced  ia 
America." 

There  are  no  known  cases  of  bud  variations  of  the  cherry, 
and  only  four  mutations  of  the  peach  out  of  2181  varieties 
described  by  Hedrick  in  "The  Peaches  of  New  York." 

Knight  records  the  case  of  a  Yellow  Magnum  Bonum  plum, 
one  branch  of  which  bore  red  Magnum  Bonum  fruits.'  A 
Coes  Golden  Drop  is  reported  by  Powell  as  producing  a 
branch  which  bears  red  fruit.  An  Isabella  grape  vineyard, 
in  California,  is  said  to  have  produced  several  mutating 
vines  which  bore  fruit  superior  in  quality  to  the  mother  plants, 
and  that  have  been  propagated  under  the  name  "Pierce." 
The  Golden  Queen  raspberry  originated  as  a  sport  from 
Cuthbert,  formerly  called  Queen  of  the  Market,  and  was 
introduced  to  public  notice  by  J.  T.  Lovett,  Little  Silver, 
New  Jersey. 

The  occurrence  of  nectarines  as  bud-sports  on  peach  trees 
is,  of  course,  common  and  has  been  observed  by  horticultur- 
ists for  a  long  time. 

Whitten  took  cions  from  a  high-  and  low-yielding  Ben 

Davis  tree  in  1895  and  has  observed  trees  propagated  from 

them  until  1917.     He  says:  "Summing  up  the  results  for 

the  entire  period  of  years  since  the  trees  came  into  bearing 

1  Munson,  W.  M.    Loc.  cil. 


322  POMOLOGY 

there  is  no  significant  difference  between  the  total  yield  of 
the  trees  of  high  yielding  parents  and  low  yielding  parents."  ^ 

Stewart  ^  reports  an  experiment  in  which  trees  showing 
marked  variation  in  yield  and  color  were  propagated  and 
planted  for  observation.  At  the  time  of  his  report,  however, 
no  progress  had  been  made  which  would  indicate  that  such 
superiority  had  been  transmitted,  thus  again  pointing  to  the 
conclusion  that  the  differences  were  due  to  environment. 

Macoun  ^  also  propagated  some  trees  which  showed 
marked  variation  in  yield,  amounting  to  100  and  200  per 
cent  difference,  and  records  were  kept  on  the  yields  from 
the  trees.  However,  no  decided  evidence  is  at  hand  after 
they  have  produced  three  crops  to  substantiate  any  claim 
that  they  will  be  superior  in  bearing. 

Extensive  observations  have  been  made  in  recent  years 
of  bud  variation  of  orange,  lemon,  and  grapefruit  trees  by 
Shamel  ^  and  others.  These  fruits,  particularly  certain  va- 
rieties, are  found  to  be  in  a  very  variable  condition,  and  bud- 
sports  are  frequently  observed  with  a  number  of  the  char- 
acters of  both  tree  and  fruit.  In  recording  the  performance 
of  the  trees,  such  characters  are  observed  as :  habits  of  growth 
of  the  trees;  characteristics  of  the  bloom;  season  and  amount 
of  production  of  fruit;  size,  shape,  and  color  of  fruit;  texture, 
thickness,  and  appearance  of  the  rind;  amount  and  quality 
of  the  juice;  and  other  tree  and  fruit  characteristics. 

Shamel  states  in  regard  to  lemon  trees  that  "The  produc- 
tive strains  in  every  case  known,  produce  a  higher  percent- 
age of  first-grade  commercial  lemons  than  the  unproductive 

1  Whitten,  J.  C.    Mo.  Agr.  Exp.  Sta.  Bull.  163.    p.  55.     1919. 

2  Stewart,  J.  P.    Penn.  Agr.  Exp.  Sta.  Bull.  134. 

3  Macoun,  W.    Dominion  Exp.  Farmers  Bull.  86.    1916. 

*  Shamel,  A.  D.  Bud  variation  in  lemons.  Jour.  Heredity,  Feb.,  1917. 
Lemon  orchard  from  buds  of  single  selected  tree.  Jour.  Heredity, 
Nov.,  1918. 


ORIGIN  AXD  IMPROVEMENT  OF  FRUIT        323 

strains.  For  example,  about  80  per  cent  of  the  crop  of  tree 
of  the  productive  strain  of  the  Eureka  variety  in  the  per- 
formance record  plots  has  been  of  the  best  grade,  while  the 
unproductive  strains  have  produced  only  about  20  per  cent 
of  the  best  grade  of  fruit."  This  statement  does  not  refer 
to  orchards  which  have  been  propagated  from  superior  trees, 
but  rather  to  superior  trees  under  observation  in  orchards. 
However,  several  citrus  orchards  are  now  in  bearing  in  Cali- 
fornia which  have  been  propagated  from  superior  trees  or 
branches,  and  according  to  their  records  give  distinct  promise 
of  ]ierpetuating  the  desirable  characters  of  the  parent  trees. 

285.  Plant  introduction. — In  colonial  times  it  was  not 
surprising  to  find  that  many  European  fruits  were  introduced 
into  America  regardless  of  their  adaptability.  As  a  result  there 
were  many  failures,^  and  not  until  seedlings  of  these  as  well  as 
of  native  sorts  began  to  appear  were  valuable  American  fruits 
secured.  The  entire  history  of  American  pomology  is  inti- 
mately associated  with  that  of  the  introduction  of  foreign  fruits. 
England,  continental  Europe,  Siberia,  Japan,  and  China  have 
all  made  contributions  to  the  present  catalogue  of  fruits. 

Perhaps  the  most  interesting  chapter  in  the  history  of 
fruit  introductions  is  that  dealing  with  the  effort  to  secure 
hartly  fruits  from  Russia.  These  fruits,  which  were  intro- 
duced during  the  70's  and  80's  of  the  last  century,  were 
heralded  as  the  solution  of  apple-growing  in  the  cold  parts  of 
the  United  States  and  Canada.  Enthusiasm  ran  high  for 
several  years,  but  at  the  present  time  few  of  the  varieties  so 
introduced  are  considered  valuable  and  the  chief  interest 
lies  in  using  their  seedlings  for  hardy  stock  on  which  to  work 
other  sorts  and  also  for  producing  new  varieties  either  from 
seedlings  or  from  crosses. 

1  Bailey,  L.  H.  Survival  of  the  Unlike.  Macmillan  Co.,  New  York. 
2nd  E(i.  1896.  Evolution  of  Our  Native  Fruits.  Macmillan  Co.,  New 
York.     1898. 


324 


POMOLOGY 


286.  Chance  seedlings. — It  is  well  known  that  the  larger 
number  of  varieties  of  the  tree-fruits  originated  as  chance 
seedlings  and  were  discovered  and  introduced  into  cultiva- 
tion by  some  observer  and  admirer  of  them.  Hedrick  and 
Wellington  ^  review  this  matter  in  regard  to  the  apple  and 
say  that  "of  the  3000  or  more  varieties  which  have  been 
described,  nearly  all,  as  their  histories  show,  have  come  from 
chance  seedlings."  Beach  describes  698  varieties  in  "The 
Apples  of  New  York"  and  of  these  "no  case  is  recorded  of  a 
variety  known  to  have  come  from  a  self-fertilized  seed." 
Even  the  seed  parent  is  given  for  only  thirty-nine  varieties 
in  all,  while  the  seed  and  pollen  parent  is  known  certainly 
for  only  one  (Ontario).  Both  parents  are  named  for  the 
Pewaukee  and  Gideon,  but  in  each  case  one  of  the  parents 
is  guessed.  Seventy-one  are  listed  as  coming  from  chance 
seedlings,  i.  e.,  from  seed  sown  without  knowledge  of  either 
parent  or  from  natural  seedlings.  The  origin  of  517  of  the 
698  varieties  is  unknown.  However,  progress  is  being  made 
and  several  new  varieties,  produced  by  breeding,  are  about 
to  be  introduced  from  some  of  the  experiment  stations. 


Table  XC 
origin  of  the  common  fruits 


Both  parents 

One  parent 

knoivn 

known 

2(?) 

39 

20 

61 

74 

57 

49 

108 

37 

214 

182 

479 

Neither  parent 
known 


Originated  as 
bud  sport 


Total 


Apple . 
Cherry 
Grape . 
Plum. . 
Peach . 


588  (?) 
1064 
72 

542 
1765 


4 
0 
0 

1 

K?) 


4031 


633 
1145 
203 
700 
2181 


4862 


1  Hedrick,   U.  P.,   and  Wellington,  R.     An  experiment  in  breeding 
apples.    N.  Y.  (Geneva)  State  Exp.  Sta.  Bull.  350.    1912. 


ORIGIN  AND  IMPROVEMENT  OF  FRUIT        325 

For  cherries,  Hedrick  has  searched  the  Uterature  and 
finds  that  httle  is  known  in  regard  to  their  origin.  The 
histories  of  the  varieties  described  in  "The  Cherries  of  New- 
York"  show  that  nearly  all  of  them  have  come  from  chance 
seedlings.  No  case  is  recorded  of  a  variety  known  to  have 
come  from  self-fertilized  seed.  The  seed  parent  is  given  for 
sixty-one  of  1145  varieties.  The  seed  and  pollen  parents  of 
twenty  of  the  cherries  described  are  given.  Of  these,  sixteen 
are  hybrids  originating  with  N.  E.  Hansen,  of  South  Dakota, 
leaving  but  four  sorts  the  parents  of  which  were  known  before 
the  recent  work  of  Hansen.  Cherries  arising  from  seed  sown 
without  knowledge  of  either  parent  or  from  natural  seedlings 
are  put  down  as  chance  seedlings.  Of  these  there  are  147. 
The  origin  of  1064  of  the  varieties  described  by  Hedrick  is 
unknown. 

In  "The  Peaches  of  New  York,"  Hedrick  describes  2181 
varieties  of  peaches,  no  one  of  which  is  known  to  have  come 
from  a  self-fertilized  seed.  The  seed  parent  is  given  for  214 
varieties;  the  seed  and  pollen  parents  for  37  varieties.  Of 
chance  seedlings,  sorts  from  seed  with  neither  parent  known, 
there  are  161.  The  origin  of  1765  out  of  a  total  of  2181 
varieties  described  is  unknown. 

287.  Work  in  Canada.^ — The  low  winter  temperatures 
and  the  relatively  short  growing  season  in  many  parts  of 
Canada  have  made  it  necessary  to  secure  varieties  of  fruits 
which  would  be  adapted  to  such  climatic  conditions.  It, 
therefore,  devolved  on  the  earlier  workers  in  that  countiy 
either  to  introduce  or  to  originate  new  varieties,  as  standard 
commercial  sorts  were  not  sufficiently  hardy. 

1  Macoun,  W.  T.  The  apple  in  Canada.  Dom.  Canada  Dept.  Agr. 
Bull.  86.  1916.  Apple  breeding  in  Canada.  Proc.  Amer.  Pom.  Soc. 
1917.  pp.  11-27.  Saunders,  Win.  Hardy  apples  for  Canadian  North- 
west. Central  Exp.  Farms.  Bull.  68.  1911.  Macoun,  W.  T.  Apple 
breeding  in  Canada.     Amer.  Breed.  Assoc,  Vol.  8,  1911.     pp.  479-487. 


•326  POMOLOGY 

Great  credit  is  due  the  amateur  and  professional  horti- 
culturists of  Canada  for  the  results  of  their  efforts  along  this 
line.  Not  only  have  they  produced  varieties  of  apples  which 
are  hardy  in  sections  where  previously  no  fruit  could  be 
grown,  but  they  have  also  arrived  at  some  conclusions  which 
will  be  of  value  to  future  plant-breeders. 

The  Central  Experimental  Farms,  where  most  of  the  work 
is  conducted,  are  located  at  Ottawa,  but  there  are  also  several 
substations  at  various  points  in  the  Dominion.  At  Ottawa, 
734  named  varieties  of  apples  have  been  tested  as  well  as 
many  unnamed  seedlings;  also  160  Russian  sorts,  though 
many  which  were  at  first  thought  to  be  different  have  proved 
to  be  identical. 

The  first  recorded  apple  breeding  in  Canada  seems  to  be 
that  of  Charles  Arnold,  of  Paris,  Ontario.  He  made  several 
crosses  between  Northern  Spy  and  Wagener  and  exhibited 
eighteen  of  the  cross-bred  apples  in  Boston  in  1873.  One  of 
these  apples,  which  was  named  Ontario,  has  attained  some 
commercial  importance. 

In  1869  Francis  Peabody  Sharp,  of  Upper  Woodstock, 
New  Brunswick,  began  some  crossing  with  apples,  having 
as  his  object  the  production  of  an  apple  of  extreme  hardiness 
and  productivity.  He  used  as  parents  the  New  Brunswicker 
— either  Oldenburg  or  very  similar  to  it — and  Fameuse  (as 
the  male).  Several  of  his  crosses  have  been  propagated,  but 
Crimson  Beauty  is  doubtless  the  best  known  and  is  most 
widely  distributed  commercially. 

The  first  extensive  work  in  growing  seedling  trees  was 
begun  in  1890  by  William  Saunders  when  an  orchard  of  about 
three  thousand  seedling  trees  was  planted.  The  seed  from 
which  these  trees  were  grown  came  from  north  of  Riga, 
Russia.  About  fifty  of  them  began  to  bear  in  1897.  "The 
number  of  trees  was  gradually  reduced  by  winter-killing,  by 
fire-blight,  or  were  removed  on  account  of  weak  growth  and 


ORIGIN  AND  IMPROVEMENT  OF  FRUIT        327 

inferior  quality.    All  but  a  few  of  those  which  fruited  were 
as  good  as  the  named  varieties  of  Russian  apples." 

Again  in  1898  a  large  number  of  seedling  trees  was  planted 
by  Macoun.  The  seeds  were  taken  from  varieties  of  standard 
quality,  such  as  Mcintosh,  St.  Lawrence,  Fameuse,  Wealthy, 
Gano,  and  Northern  Spy.  Excellent  results  were  obtained, 
and  in  1916  he  reported  that  "During  the  past  twelve  years, 
1211  of  these  seedling  varieties  have  fruited,  and  of  these, 
83.30  per  cent  were  of  marketable  size  (medium  to  large) 
and  only  3.95  per  cent  were  small  or  crab-like.  Of  the  1211 
varieties,  there  have  been  378  considered  so  promising  that 
they  are  being  propagated  for  further  test  and  99  of  the  best 
have  been  named."  Some  of  the  hardiest  of  his  apples  have 
fruited  as  far  north  as  latitude  58°,  at  Fort  Vermilion  on 
Peace  River. 

In  addition  to  this  work,  a  somewhat  different  procedure 
was  followed  by  Macoun  in  1910.  Seed  was  saved  of  the 
hardiest  Russian  apples,  including  Transparent,  Charlamoff, 
Oldenburg,  Tetofsky,  and  Hibernal.  The  seedling  trees  were 
sent  to  the  prairie  provinces,  where  the  winters  are  particu- 
larly severe,  and  planted  in  nurseiy  rows.  After  three  years, 
any  that  survived  the  winter  were  transplanted  to  an  orchard 
for  further  trial,  and  in  this  way  the  hardiest  trees  were 
selected  and  those  producing  worthy  fruit  were  retained  for 
propagation. 

Special  work  is  also  being  conducted  with  crossing  and 
hybridizing  apples.  Preliminary  studies  are  being  made  on 
the  transmission  of  fruit  characters  as  a  basis  for  future 
investigation.  This  work  in  crossing  was  begun  by  William 
Saunders  about  1894.  He  introduced  the  berried  crab  {Pyrus 
hnccata)  from  Russia  several  years  before;  and  after  deter- 
mining its  hardiness  he  made  crosses  between  that  species 
and  many  of  the  best  and  hardiest  sorts  of  apples  (P.  Mains) 
grown  in  Ontario.     In  1896  he  used  another  hardy  wild 


328  POMOLOGY 

crab,  known  as  P.  prunifolia,  in  his  crosses.  The  best  hy- 
brids obtained  from  these  crosses  with  P.  haccata  and  P. 
prunifolia  were  again  crossed  with  the  large  fruited  P.  Mains 
and  thus  he  introduced  a  second  quota  of  "blood"  of  the 
larger  varieties.  Several  of  these  second  crosses  are  now 
fruiting  and  are  promising  sorts. 

From  the  work  in  Canada  the  following  conclusions  are 
reached  in  regard  to  originating  new  varieties  of  apples: 

1.  To  produce  a  hardy  apple  where  no  apples  have  yet 
been  hardy:  (a)  cross  the  apple  with  the  wild  Siberian  crab 
(Pijriis  haccata) ;  (b)  sow  seeds  of  apples  which  have  ripened 
in  a  climate  as  nearly  similar  as  possible. 

2.  To  produce  a  hardy  long-keeping  apple  of  good  quality: 
sow  seeds  of  long-keeping  varieties  of  good  quality  of  which 
both  parents  are  long-keeping. 

3.  To  produce  an  apple  having  certain  characteristics,  as 
regards  hardiness,  vigor,  and  productiveness  of  tree,  and 
quality,  size,  and  appearance  of  fruit:  sow  seeds  of  varieties 
having  most  of  the  characteristics  desired. 

4.  In  cross-breeding  apples  where  quality  is  an  important 
factor,  as  it  should  be  in  most  places,  cross  two  varieties 
which  are  both  good  or  very  good  in  quality.  It  has  been 
the  experience  at  Ottawa  that  in  crossing  a  variety  of  good 
quality  with  one  inferior,  the  crosses  will  nearly  always  bear 
fruit  of  a  quality  inferior  to  that  of  the  better  parent. 

288.  Work  of  Peter  Gideon  and  other  pioneers  in  the 
United  States. — The  name  of  Peter  Gideon  will  always 
be  associated  with  the  early  struggles  to  produce  an  apple 
which  would  be  of  good  quality  and  hardy  enough  to  with- 
stand the  severe  climate  of  the  Upper  Mississippi  Valley. 
His  work  continued  for  more  than  thirty  years,  in  which 
time  he  grew  thousands  of  seedlings  of  apple,  peach,  plum, 
and  cherry,  and  shortly  before  his  death  (1899)  he  wrote 
that  of  all  these  thousands  of  seedlings  and  named  varieties 


ORIGIN  AND  IMPROVEMENT  OF  FRUIT        329 

of  fruits  tested,  "only  two  trees  remain."  "One  of  these, 
the  Wealthy,  grown  from  a  cherry-crab  seed,  obtained  from 
Albert  Emerson,  of  Bangor,  Maine,  of  whom  I  obtained 
scions  at  the  same  time,  from  which  I  grew  the  Duchess, 
Blue  Peannain,  and  the  cheriy-crab,  all  of  which,  combined, 
were  the  foundation  of  Minnesota  horticulture,  that  to-day 
is  the  pride  and  hope  of  the  Northwest."  ^  "Thus  far  it 
has  taken  from  three  to  five  hundred  seedlings  to  give  us 
one  first-class  apple,  and  from  seed  taken  from  the  best 
apples  we  had." 

Patten,  Watrous,  and  others  of  Iowa  and  the  Central  West 
also  contributed  much  of  the  foundation  work  in  securing 
hardy  fruits  for  the  prairie  states. 

289.  Hansen  hybrids. — N.  E.  Hansen  of  South  Dakota 
has  effected  many  inter-specific  combinations  between 
Prunus  Besseyi,  the  western  sand  cherry,  as  one  parent  and 
varieties  of  P.  salicina  or  P.  Munsoniana  as  the  other;  and 
other  combinations  have  also  been  made.  In  these  "Hansen 
hybrids"  a  new  tyi^e  of  plum  has  come  into  use  in  the  North- 
west. While  these  sand  cheriy  crosses  have  been  experi- 
mented with  for  some  time,  the  success  of  the  variety  "Com- 
pass" cherry  has  added  impetus  to  the  movement.  While 
the  saad  cherry  is  one  of  the  parents  of  these  crosses,  they 
in  reality  are  not  cherries  but  plums.  One  of  the  outstanding 
characteristics  of  these  hybrids  is  the  profuse  early  fruiting 
habit.  They  often  bear  at  three  years  of  age  and  as  they 
grow  best  in  bush  form  and  fruit  on  the  terminal  shoots, 
winter-killing  affects  them  less.  Under  the  prairie  conditions 
of  the  Upper  Mississippi  Valley  in  the  United  States  and 
Canada,  varieties  like  Sapa,  Opata,  Etopa,  Wakapa,  and 
Okiya  have  been  a  boon  to  the  homesteader.  These  fruits 
rot  easily  and  cannot  be  shipped  for  long  distances,  but  for 

'  Some  doubt  exists  in  regard  to  the  source  of  the  seed  which  procUiced 
the  Wealthy  apple,  as  is  reported  in  Minn.  Hort.    1917.    p.  85. 


330  POMOLOGY 

home  use  they  have  filled  a  need  in  regions  where  other  plums 
could  not  be  grown.  This  tribe  is  of  special  interest  also 
because  of  its  hybrid  origin  and  suggests  the  promise  to  new 
regions  which  such  combinations  may  have.  From  this  work 
of  Hansen,  the  Northwest  has  profited  by  varieties  of  many 
fruits  and  his  work  shows  clearly  what  can  be  accomplished 
in  horticulture  by  breeding. 

290.  Burbank's  work. — The  life  and  work  of  Luther 
Burbank  of  Santa  Rosa,  California,  has  been  a  great  stimulus 
to  plant-breeding.  This  is  doubtless  due  to  the  great  novelty 
of  his  creations  and  to  the  extent  of  his  work.  He  has  ever 
held  in  mind  the  production  of  fruits  and  other  plants  which 
would  be  of  the  greatest  use  and  economic  value  and  has 
held  as  secondaiy  the  accumulation  of  scientific  data. 

Perhaps  pomology  has  profited  more  from  his  introduction 
of  Japanese  plums,  and  the  seedlings  and  hybrids  which  he 
has  obtained  from  them,  than  from  any  other  achievement. 
He  has  succeeded  in  hybridizing  diverse  forms  of  fruits,  some 
valuable  for  commercial  purposes  and  others  as  novelties. 

291.  Inheritance  of  characters  in  the  apple. — One  of  the 
few  definite  experiments  in  breeding  apples,  which  has  thrown 
some  light  on  the  inheritance  of  characters,  is  the  one  con- 
ducted by  Hedrick  and  Wellington.^  The  results  not  only 
throw  light  on  some  of  the  laws  of  inheritance  of  apples  but 
also  furnish  some  practical  results  in  the  way  of  promising 
new  varieties. 

There  were  148  crosses  made  between  standard  varieties 
in  1898  and  1899.  The  seedling  trees  began  fruiting  in  1908 
but  the  grafts  from  them  four  years  earlier.  Crosses  were 
made  between  Ben  Davis,  as  the  female  parent,  and  Esopus, 
Green  Newtown,  Jonathan,  Mcintosh,  and  Mother;  between 
Esopus  as  the  female  and  Ben  Davis  and  Jonathan;  Mcin- 
tosh and  Lawver;  Ralls  and  Northern  Spy;  Rome  and  North- 
^  Loc.  cil. 


ORIGIN  AND  IMPROVEMENT  OF  FRUIT        331 

ern  Spy;  and  Sutton  and  Northern  Spy.  Some  of  the  im- 
portant observations  by  the  authors  as  a  result  of  the  work 
are  as  follows:  (1)  These  crosses  strikingly  contradict  the 
idea  that  seedling  apples  (of  cultivated  sorts)  revert  to  the 
wild  prototype.  (2)  The  stimulus  of  hybridity  is  very 
marked  in  the  vigor  of  the  crosses  under  consideration. 
(3)  The  behavior  of  some  of  the  crosses  strongly  suggests 
that  apples  may  be  "preponent"  in  one  or  more  of  their 
characters. 

Other  conclusions  which  bear  on  the  laws  of  inheritance 
are: 

In  color  of  skin,  the  fruits  in  which  yellow  predominates 
over  red  seem  from  the  data  to  be  in  a  heterozygous  condition 
for  yellow  and  red.  The  fruits  in  which  red  predominates 
are  either  homozygous  or  heterozygous.  The  pure  yellows 
are  homozygous. 

The  data  favor  the  supposition  that  so  far  as  size  and 
shape  are  concerned,  these  characters  are  inherited  practically 
as  intermediates. 

While  all  the  varieties  were  sub-acid,  the  progeny  indicate 
strongly  that  crosses  of  these  sub-acid  varieties  break  up  in 
the  proportion  of  three  sour  apples  to  one  sweet  one. 

292.  The  heterozygous  nature  of  fruits. — If  an  individual 
plant  is  pure  or  homozygous  for  any  one  or  all  of  its  charac- 
ters, then  all  of  the  sexual  gametes  produced  by  it  would,  if 
the  plant  is  self -fertilized,  produce  progeny  which  are  alike. 
Thus,  if  a  Grimes  Golden  apple  were  homozygous  for  all 
of  its  characters  when  self-fertilized,  all  the  seedling  trees 
produced  would  be  practically  identical  with  the  parent. 
Such  a  condition  does  not  exist,  however,  for  the  seeds  of  a 
self-fertilized  apple  tree  will  produce  a  motley  array  of  prog- 
eny, varjing  in  color,  form,  quality,  and  tree  characters. 
Therefore,  all  of  the  common  varieties  are  heterozygous  and 
may  be  regarded  as  the  Fi  generation  of  previous  crosses. 


332  POMOLOGY 

It  so  happens,  however,  that  it  makes  no  practical  difference 
whether  fruit  varieties  are  homozygous  or  heterozygous  since 
a  valuable  new  kind  is  propagated  asexually  and  hence  has 
little  opportunity  to  break  up,  or  lose  its  type.  Therefore,  it 
is  unnecessary  in  breeding  fruits  to  take  this  into  considera- 
tion and  in  crosses  between  heterozygous  parents  the  re- 
combination of  characters  takes  place  in  the  Fi.  This  being 
the  case,  new  combinations  can  be  obtained  from  which  to 
select  desirable  fruiting  types  without  selfing  individuals  and 
encountering  sterility  or  the  great  reduction  in  vigor  which 
so  often  happens. 

293.  Pedigreed  nursery  stock. — Following  the  usage  of 
the  animal-breeders,  certain  nurserymen  have  adopted  the 
term  "pedigreed"  to  designate  fruit-trees  which  have  been 
propagated  from  a  tree  of  known  behavior  or  superior  worth. 
This,  of  course,  carries  with  it  the  idea  that  such  trees  will 
be  better  producers,  have  better  color  and  quality,  or  have 
some  other  merit  which  individuals  of  the  same  variety 
selected  at  random  would  not  possess. 

It  must  be  remembered  that  animal-breeders  always  refer 
to  a  new  individual  produced  by  the  union  of  sex  cells  while 
the  nurseiyman  refers  to  the  same  identical  tree  which  has 
been  increased  by  asexual  propagation.  Therefore,  unless  a 
true  mutation  occurs,  the  varying  forms  of  a  fruit  variety 
will  not  be  transmitted  by  vegetative  propagation.  Owing 
to  the  failure  of  practically  all  the  experiments  in  the  eastern 
United  States  to  secure  a  superior  strain  of  trees  by  prop- 
agating from  a  high  producer  or  othenvise  superior  plant, 
there  is  a  distinct  prejudice  among  horticulturists  to  the 
use  of  the  term  ''pedigreed"  trees.  On  the  other  hand,  the 
cases  cited  from  California  show  that  many  true  bud-sports 
do  occur  in  that  state,  and  Coit  has  adopted  the  use  of  a 
better  term  to  designate  trees  propagated  from  these  mutants 
in  the  phrase  "recorded  trees." 


ORIGIN  AND  IMPROVEMENT  OF  FRUIT        333 

Nurseiymen  and  fruit-growers  will  continue  to  search  for 
superior  strains  of  the  old  varieties  and  it  cannot  now  be 
stated  with  absolute  assurance  that  some  success  will  not 
crown  their  efforts. 

294.  Graft-hybrids^  represent  one  of  the  most  interesting 
phenomena  that  occurs  in  nature.  They  remained  unex- 
plained for  centuries  although  many  of  them  had  been  ob- 
served. A  graft-hybrid  may  be  defined  as  the  combination 
of  the  stock  and  cion  tissues  into  a  form  which  is  intermediate 
between  the  two.  The  explanation  for  these  queer  ''freaks" 
or  chimeras  was  not  clear  until  they  had  been  produced 
artificially.  It  appears  that  either  there  is  a  mingling  of 
the  tissues  at  the  point  of  contact  of  the  graft  or  else  that  an 
adventitious  bud  arises  where  the  callous  has  formed,  which 
partakes  of  both  tissues.  The  result  is  either  a  pcriclinal 
chimera  in  which  one  tissue  envelops  the  other  (the  hand-in- 
glovc  type)  or  a  sectorial  chimera  in  which  the  two  tissues 
occur  side  by  side  on  the  same  stem,  leaf,  or  flower,  yet  each 
retains  its  independent  form.  In  at  least  one  case,  the 
number  of  chromosomes  in  the  graft-hybrid  is  the  same  as 
if  the  hybrid  were  sexual  in  nature,  thus  being  a  true  hybrid. 

An  apple  called  Sweet  and  Sour,  which  is  described  in 
"The  Apples  of  New  York"  and  is  occasionally  seen,  is 
probably  a  graft-hybrid.  The  apple  is  somewhat  ribbed 
and  this  ribbed  portion  is  green  while  the  part  between  is 
yellowish.  The  flesh  beneath  the  green  skin  is  distinctly 
acid,  while  that  under  the  j^ellowish  skin  is  mildly  sub-acid 
or  sweetish. 

295.  Breeding  the  grape. — The  early  varieties  of  Amer- 
ican grapes  wcr(>  s(>cdlings  of  merit  derived  principally  from 
Vitis  Labrusca.     The  early  efforts  to  grow  the  European 

*  Popenoe,  Paul.  Plant  chimeras.  Jour.  Heredity,  Vol.  5,  p.  521. 
Dec,  1914.  Ca.stle,  W.  E.  An  apple  chimera.  Jour.  Heredity,  Vol. 
5,  pp.  200-202.    1914. 


334  POMOLOGY 

grape  (F.  vinifera)  in  eastern  United  States  failed  utterly, 
but  on  the  Pacific  Coast  they  have  been  successful  since 
the  early  Mission  days.  Recently  Hedrick  has  succeeded 
in  establishing  V.  vinifera  in  New  York  state  where  several 
are  proving  capable  of  withstanding  the  climate  except  that 
some  winter  protection  must  be  given. 

In  general,  the  breeding  work  that  has  been  done  with 
grapes,  covering  the  period  since  the  introduction  of  the 
Isabella  (1816)  and  Catawba  (1823)  up  to  the  present  time, 
is  one  of  the  most  valuable  chapters  in  the  history  of  breeding 
fruits  in  this  country. 

296.  Inheritance  of  self-sterility  in  grapes. — It  will  be 
recalled  that  grape  varieties  differ  in  regard  to  the  structure 
of  their  flowers.  They  are  classified  as  (1)  true  hermaphro- 
dites, (2)  hermaphrodites  functioning  as  females,  owing  to 
completely  or  partially  abortive  pollen,  and  (3)  pure  males 
with  the  pistils  absent  or  rudimentary.  There  are  also  two 
distinct  types  of  stamens  among  these  classes:  (1)  those 
which  are  upright,  and  such  varieties  are  practically  always 
self-fertile ;  and  (2)  those  which  are  reflexed  or  bent  backward 
and  downward  which  are  self-sterile.  Of  the  132  important 
commercial  varieties  of  the  grape  described  in  "The  Grapes 
of  New  York,"  Dorsey  (1909)  shows  that  95  have  upright 
stamens  and  37  reflexed.  The  question  arises  as  to  whether 
this  character  of  the  stamens  will  behave  as  a  unit  character 
or,  in  other  words,  whether  self-sterility  can  be  eliminated 
by  breeding. 

297.  The  inheritance  of  sex  in  the  grape. — In  the  grape 
the  flower  type  has  such  an  important  economic  bearing  that 
considerable  attention  has  been  given  to  the  inheritance  of 
flower  type  or  sex.  Since  the  wild  vines  are  dioecious  for 
the  most  part,  the  question  has  often  been  raised  as  to  the 
origin  of  the  perfect  or  hermaphrodite  flower  type  such  as 
is  found  in  Concord.    Some  recent  investigations  have  thrown 


ORIGIN  AND  IMPROVEMENT  OF  FRUIT        335 

light  on  this  question.     When  the  data  of  Hedrick  and 
Anthony  ^  are  presented  according  to  the  formula 
by  Valleau,  the  following  ratios  are  obtained: 


Table  XCI 
flower  types  and  ratios  obtained  in  grape  crosses 


Formula  of  the 

genetic 
con.flilulion 

Flower  types  of  the  progeny 

IMrentis 

Hermaphrodite 

Female 

Male 

types 

Upright  X  Upright 

Upright  selfetl  (same 

FH  xFH 

FHxFH 
FFxFF 
FFxFH 

FF  X  FF 
GF  X  FM 

180 

673 

16 

207 

94 

7 

47 

1.52 

16 

206 

73 

6 

0 

0 
0 
0 

0 
9 

3.8  :  1 

Reflexed  x  Reflexed .... 

Reflexed  x  Upright 

Upright  x  Reflexed 
(cro.ss  not  made) 

Reflexed  selfod 

Upright  X  Wikl  male  .  .  . 

1  :  1 
1  :  1 

1.2  :  1 
1:1:2 

The  apijearance  of  the  large  number  of  hermaphrodite 
seedlings  in  these  crosses  is  of  great  importance  to  grape- 
growers,  because  it  is  possible  to  select  seedlings  which  will 
be  self -fertile. 

In  crosses  made  between  varieties  of  another  species,  Vitis 
rot imdi folia,  Detjen  -  presents  data  which  throw  some  light 
on  the  first  appearance  of  the  hermaphrodite  flower  in  a 
dioecious  species.  This  is  epochal  in  southern  grape-growing 
because  it  had  heretofore  been  necessary  to  grow  unproduc- 
tive male  vines  in  vineyards  in  order  to  secure  proper 
pollination.  His  evidence  is  so  clear  cut  on  this  point  that 
some  of  it  will  be  included  here  in  a  condensed  form  for  the 
convenience  of  the  student : 

1  Hedrick,  U.  P.,  and  Anthony,  R.  D.  Inheritance  of  certain  char- 
acters of  grapes.  Jour.  Agr.  Res.  4:  315-330.  1915;  also  N.  Y.  State 
Agr.  Exp.  Sta.  Bull.  Tech.  45.  Valleau,  W.  D.  Inheritance  of  sex  in 
the  grape.    Amer.  Nat.  50:  554-564.    1916. 

-  Detjen,  L.  R.  Inheritance  of  sex  in  Vitis  rotundifolia.  N.  C.  Agr. 
Exp.  Sta.  Tech.  BuU.  12.    1917. 


336 


POMOLOGY 


Table  XCII 

FLOWER  TYPES  AND  RATIOS  OBTAINED  IN  CROSSES  IN  Vitis  TOtundifoUa 


Flower  type 

Cross 

Hermaphrodites 

Females 

Males 

Female  x  male        .  . 

0 

348 
197 
79 

1420 
461 

228 
74 

1509 

Scuppernong  x  Hope 

0 

Thomas  x  Hope 

James  x  Hope 

0 
0 

The  great  contrast  in  the  number  of  hermaphrodite  vines 
bearing  flowers  with  upright  stamens  when  Hope  is  taken 
as  a  pollen  parent  and  when  male  vines  are  so  used  is  out- 
standing. Hope  was  found  in  the  wild  in  1910  and  differs 
from  the  typical  male  vine  in  that  it  has  a  partially  developed 
pistil.  Its  genetic  constitution  is  shown  by  its  behavior  in 
crosses  in  which  it  is  seen  to  be  decidedly  different  from 
others  of  its  kind. 

In  the  instances  cited  here,  there  is  an  excellent  illustra- 
tion of  the  solution  of  the  commercial  problem  of  sterility 
in  the  grape  by  breeding.  Contributions  like  these  to  the 
knowledge  of  horticultural  plants  will  have  a  far  reaching 
influence  on  practice. 

298.  Rogers'  hybrids. — The  work  of  Rogers  in  hybridiz- 
ing the  native  American  grape  with  the  European  is  epochal 
in  the  histoiy  as  well  as  in  the  commercial  status  of  the 
grape.  Rogers  conducted  his  breeding  work  at  Salem,  Massa- 
chusetts, during  the  early  1850's.  As  a  result  of  hybridizing 
large-fruited  Labrusca  grapes  with  the  Black  Hamburg  and 
White  Chasselas,  both  vinifera  varieties,  he  secured  about 
150  seedling  plants  but  only  raised  45  to  maturity.  They 
were  tested  by  himself  and  others,  being  known  by  numbers, 
from  1  to  45,  but  several  were  later  named  for  persons  of 
note  in  science  or  for  other  attainments,  as  well  as  for  counties 


ORIGIN  AND  IMPROVEMENT  OF  FRUIT        337 

and  towns  of  Massachusetts.  The  named  varieties  which 
are  now  grown  commercially  are  Goethe,  Massasoit,  Wilder, 
Lindley,  Gaertner,  Agawam,  Merrimac,  Requa,  Aminia, 
Essex,  Bariy,  and  Herbert.  These  grapes  are  of  exception- 
ally high  quality,  combining  the  richness  of  the  European 
with  the  general  type  of  the  American  grape;  but  unfortu- 
nately these  hybrids  are  usually  somewhat  deficient  in  vigor, 
hardiness  of  root  or  vine,  self-fertility  or  pi'oductiveness. 

299.  Breeding  disease-resistant  fruits. — Most  of  the 
definitely  plamied  experiments  in  breeding  of  deciduous 
fruit-trees  in  the  United  States  and  Canada  have  had  as 
their  purpose  the  securing  of  hardier  varieties.  Of  equal 
importance  to  the  orchardists  of  the  large  fruit  regions  of 
this  country  is  the  problem  of  securing  fruits  resistant  to 
such  diseases  as  blight  {Bacillus  amylovorus),  peach  yellows, 
and  the  like,  and  breeding  seems  to  be  the  ray  of  hope  to 
these  breeders.  The  selection  of  disease-resistant  individuals 
would  be  the  first  means  of  attacking  this  problem,  since 
man}^  other  kinds  of  plants  have  produced  disease-resistant 
strains,  as  for  example,  flax,  cotton,  and  melons.  In  these 
genera,  however,  there  is  a  new  sexual  generation  each  year, 
which  affords  an  opportunity  for  variation  that  does  not 
obtain  within  a  clone.  It,  therefore,  remains  for  the  breeder 
to  combine  a  variety  or  species  which  is  immune  to  the 
trouble  in  question  with  a  variety  of  commercial  importance 
subject  to  it.  Thus,  if  a  Bartlett  subject  to  blight  is  crossed 
or  hybridized  with  a  blight-free  pear,  there  is  a  possibility 
of  obtaining  a  fruit  as  valuable  as  the  Bartlett  but  with  the 
"factor"  for  blighting  absent.  This  possibility  rests  on  the 
assumption  that  disease-resistance  or  susceptibihty  is  a  unit 
character  and  thus  jiermits  of  recombination. 

300.  Stocks  for  pears. — According  to  the  findings  of 
Reimer,  the  following  species  of  pear  are  quite  blight- 
resistant:  Pyrus  sinensis,  P.  ovoidea,  and  P.  Pashia  {vario- 


338  POMOLOGY 

losa).  While  he  records  that  P.  betulcefolia  is  somewhat 
susceptible  to  blight  in  Oregon,  it  has  been  remarkably  free 
in  South  Dakota  where  it  has  been  grown  for  twenty  years, 
and  in  the  trial  plots  at  Washington,  D,  C, 

Pyrus  Calleryana  is  a  recently  described  species  of  pear 
native  to  China  which  is  veiy  promising  as  a  stock.  Hence, 
if  a  variety  of  high  quality  can  be  produced  by  hybridizing 
P.  communis  (from  which  all  the  commonly  grown  pears 
originated)  with  one  of  the  hardy,  blight-resistant  species, 
the  solution  to  one  of  the  most  serious  problems  in  pomology 
would  be  at  hand. 

Hansen  has  crossed  P.  sinensis  and  P.  betulcefolia  with 
several  of  the  best  cultivated  pears  (P.  communis)  and  dis- 
tributed thirty-nine  promising  sorts  throughout  several  states 
for  trial.  It  is  hoped  that  they  may  prove  to  be  the  basis  of 
pear  breeding  to  secure  valuable  varieties  immune  to  blight.^ 

301.  Stock  for  grapes. — What  appears  to  be  a  clear  case 
of  the  Mendelian  behavior  of  disease-resistance  is  seen  in 
the  work  of  Rasmuson  ^  who  attempted  to  secure  varieties 
of  V.  vinifera  which  would  be  immune  to  the  great  scourge 
of  phylloxera.  He  made  crosses  between  certain  American 
species  and  V.  vinifera,  and  also  crosses  between  different 
varieties  of  V.  vinifera.  In  studying  the  F2  generation  of 
these  crosses,  he  found  that  the  vinifera  crosses  yielded  off- 
spring susceptible  to  the  disease  while  crosses  between  the 
American  species  and  vinifera  yielded  varieties  part  of  which 
were  resistant  and  part  susceptible,  but  the  latter  were  in 
the  minority.  The  fact  that  disease-resistance  proved  to 
be  dominant  and  susceptibility  recessive  in  the  progeny  of 
this  latter  set  of  crosses,  bodes  well  for  the  future. 

1  Reimer,  F.  C.  Proc.  Amer.  Pom.  Soc.  1915.  Hansen,  N.  E. 
S.  D.  Agr.  Exp.  Sta.  Bull.  159.  1915.  Galloway,  B.  T.  Jour.  Heredity, 
Vol.  9.    Jan.,  1920. 

2E.S.R.  36:537. 


CHAPTER  XIV 
PROPAGATION  AND  FRUIT-STOCKS 

Since  most  of  the  tree-fruits  do  not  come  ''true"  from 
seed,  it  is  necessary  to  provide  a  root  or  stock  on  which  to 
bud  or  graft  them.  The  term  "fruit-stocks,"  therefore,  re- 
fers to  the  seedhngs  on  which  are  "worked"  varieties  of  the 
tree-fruits,  nuts,  and  sometimes  grapes.  This  is  in  distinction 
to  "cion"  which  refers  to  the  piece  of  wood  of  the  desired 
variety  introduced  on  the  seedling  stock. 

The  entire  fruit-stock  situation  is  not  well  worked  out, 
as  miscellaneous  seedlings  of  unknown  genetic  constitution 
are  used.^  The  seedlings,  however,  have  given  very  good 
results,  and  the  improvements  that  could  be  made  by  a 
more  intelligent  selection  of  material  must  remain  a  con- 
jecture. Certainly  as  regards  hardiness,  disease,  and  insect 
resistance,  improvements  of  note  could  be  accomplished. 
Already  something  has  been  undertaken  and  the  proper 
organization  for  a  further  extension  of  this  work  is  now  in 
existence.  However,  as  referred  to  later,  the  relation  of 
stock  and  cion  is  only  meagerly  understood. 

302.  Handling  the  seed  and  stock. — After  the  fruit-seeds 
have  been  collected  in  the  fall,  they  are  assembled  at  the 
nurseries,  either  at  foreign  points  or  in  this  country,  where 
they  are  properly  handled  for  the  raising  of  seedling  stock. 
Apple  seed  is  secured  by  washing  pomace  obtained  at  cider 
mills  and  it  is  then  dried  in  the  open  air.  The  seed  is  then 
stratified  in  sand  until  early  spring.  The  apple  seed  will 
^See  Chapter  XIII. 


340  POMOLOGY 

usually  begin  to  sprout  rather  early  in  the  spring,  when  it 
should  be  sown  in  a  well  prepared,  deep,  rich  soil.  This  is 
important  in  order  to  produce  straight  long  roots,  as  these 
are  superior  for  propagation  purposes.  The  seed  is  sown  in 
rows  four  feet  apart  and  the  seedlings  should  be  cultivated 
thoroughly  throughout  the  summer.  After  the  leaves  have 
dropped  in  the  fall,  the  little  trees  are  dug,  a  part  of  the  tops 
removed  (leaving  about  six  inches  of  the  stem),  the  plants 
tied  in  bundles,  and  the  bundles  packed  in  boxes  of  green 
sawdust,  sand,  or  other  material  in  which  they  may  be  kept 
reasonably  moist  and  cool.  Such  seedling  roots  are  known 
as  apple  "stock." 

303.  The  more  common  fruit-stocks.— The  stock  used 
for  propagating  a  fruit  must  be  "congenial,"  that  is,  the 
cion  must  be  capable  of  making  a  good  union  and  growth  on 
such  stock.  A  number  of  unusual  combinations  can  be  made, 
but  the  more  common  are  here  listed : 

Apple — French  crab;  Vermont  crab;  Minnesota  crab; 
Virginia  crab;  and  for  dwarfing,  Paradise  and  Doucin. 

Pear — French  pear  seed;  Japan  pear;  Kieffer  seed  collected 
in  eastern  United  States.  For  dwarfing,  Angers  or  other 
quince. 

Quince — from  cuttings,  stools,  or  mound-layering;  and 
seed  (to  a  limited  extent). 

Peach — seeds  of  wild  or  standard  varieties,  usually  se- 
cured in  this  country. 

•Plum — seedlings  of  Primus  domestica;  St.  Julien;  myro- 
bolan  (P.  cerasifera) ;  and  sometimes  P.  americana.  The 
peach  may  be  used  for  plum  stock  when  the  latter  is  to  be 
grown  on  light  soils.  For  dwarfing  myrobolan,  also  mira- 
bella  (a  form  of  P.  cerasifera),  and  several  forms  of  the  native 
plums. 

Cherry — Mazzard  cherry  (P.  avium);  P.  Mahaleb  and  P. 
pennsylvanica  to  some  extent. 


PROPAGATION  AND  FRUIT- STOCKS  341 

304.  Apple  stocks. — A  change  or  adaptation  of  the 
nursery-stock  situation  is  taking  place,  owing  to  the  partial 
exclusion  of  stock  formerly  imported  from  foreign  countries. 
However,  the  following  are  in  use  at  present, 
as  indicated  above. 

French  crab  {Pijrus  Mains,  Limi.)  is  most 
commonly  used  for  the  apple,  whether  the 
seedlings  are  grown  in  France  and  then  im- 
ported to  the  United  States,  or  whether  the 
seed  is  imported  and  the  stock  grown  in  this 
country.  It  is  estimated  that  about  40  per 
cent  of  the  apple  stock  used  in  this  country  is 
imported  from  France  at  the  present  time. 
(See  Fig.  37.)  Howard  ^  answers  the  question 
as  to  what  French  stock  is  by  quoting  a  French 
nurseiyman,  as  follows: 

"The  crab  apple  seed  comes  from  Pijrus 
Malus,  Linn.  {Mains  communis,  DC.)  which 
is  simply  a  natural  apple.  This  is  a  cider 
apple.  Although  there  are  numerous  grafted 
varieties  none  but  the  cider  apple  is  used  from 
which  to  procure  seed.  Occasionally  small 
quantities  of  seeds  from  grafted  varieties  may 
become  mixed  with  the  crab  seed  but  thisp^^  37 -French 
makes  the  latter  less  valuable  as  such  seeds  ^rab,  imported 
do  not  give  satisfactory  results  for  the  pro-  apple  seedling. 
duction  of  seedlings. 

''The  apples  from  which  we  get  our  seed  are  used  for 
cider-making  purposes.  Seed  collectors  go  to  the  mills  and 
to  the  fanns  and  wash  the  pomace  that  is  left  after  the 
juice  has  been  pressed  out  and  the  seed  thus  secured  are 
dried  in  the  open  air. 

"Small  quantities  of  apple  seed  come  from  Germany  and 

1  Howard,  W.  L.    Plant  propagation.    Pub.  by  Univ.  of  Mo.    1914. 


342  POMOLOGY 

even  Russia  and  Austria,  but  France  is  known  to  be  the  one 
great  exporter  of  tiiis  seed.  Apple  seedlings  are  sold  by 
dealers  in  Holland  and  the  industry  seems  to  have  grown 
there  during  the  last  few  years  although  the  Dutch  seedlings 
are  much  inferior  to  the  French. 

"The  grower  generally  receives  his  apple  seed  in  January, 
places  it  in  a  veiy  sheltered  spot — often  in  a  stable — thor- 
oughly mixed  with  damp  river  sand.  The  sand  is  kept 
moist  and  occasionallj''  the  mixture  of  sand  and  seeds  is 
stirred.  When  the  seeds  begin  to  swell — which  will  be  in 
about  four  weeks — ^they  are  either  placed  in  cold  beds  for 
transplanting  or  sown  directly  in  the  field.  In  three  or  four 
weeks  they  begin  to  come  up.  By  soaking  in  lukewarm 
water  before  planting  the  seeds  may  be  caused  to  germinate 
quicker,  but  I  consider  it  to  be  better  to  follow  the  more 
natural  plan  and  not  force  the  seeds. 

"We  never  use  ice.  A  few  growers  soak  the  seed  for  a 
period  of  two  days  at  the  most,  but  this  practice  is  far  from 
being  common  and  is  resorted  to  only  when  the  season  is 
advanced  and  it  seems  necessary  to  hurry  the  germination." 

Vermont  crab  stock  is  raised  from  seed  collected  at  the 
cider  mills  of  New  England.  In  the  past  it  was  obtained 
largely  from  the  pomace  of  seedling  apples  which  abounded 
in  the  rough  pastures,  around  stone  walls,  and  even  in  the 
woods.  There  was  also  mixed  with  the  "wild"  apples,  fruit 
of  grafted  varieties,  often  of  poor  grade.  However,  the  fact 
that  the  seedling  apples  and  uncared-for  orchards  of  New 
England  are  rapidly  passing  out  makes  this  stock  of  no  great 
consequence  in  the  trade. 

Virginia  and  Minnesota  crabs  are  grown  from  seed  col- 
lected at  the  cider  mills  in  these  states  and  in  the  past  were 
used  to  a  considerable  extent,  but  at  present  the  French 
crab  stock  has  largely  replaced  them. 

For  dwarfing,  the  Paradise  and  Doucin  stocks  have  long 


PROPAGATION  AND  FRUIT-STOCKS  343 

been  employed.  The  usual  understanding  has  been  that  the 
former  produced  a  ''full  dwarf"  tree  and  the  latter  a  "half 
dwarf";  however,  there  seems  to  be  much  confusion  in  re- 
gard to  these  terms.  ''The  original  significant  distinction 
betwixt  the  true  Paradise  or  dwarfing  apple  stock  and  the 
true  crab  or  free  growing  stock,  had  imperceptibly  changed 
to  a  distinction  in  method  of  propagation,  all  those  apple 
stocks  which  were  raised  vegetatively  (from  layers)  being 
known  as  'Paradise,'  and  those  raised  sexually  (from  seed) 
being  known  as  'Crab.'  "  ^  The  work  of  Hatton  shows  that 
in  a  lot  of  seedlings  from  crab  and  "Paradise"  stock,  there 
will  be  in  each  both  surface  and  deep-rooted  plaiits.  It 
also  indicates  that  in  lots  of  Paradise  stock  collected  at 
various  places  in  England  and  on  the  Continent,  there  were 
"  17  distinct  types,  easily  distinguishable  botanically,  and 
varying  in  health  and  vigour  of  growth  from  the  very  dwarf 
French  Paradise,  which  on  our  soil  dies  out  with  apple 
canker  in  a  few  years,  through  intermediate  types  such  as 
the  Doucin,  moderate  and  sturdy  in  growth  and  precocious 
in  cropping,  to  the  veiy  vigorous  forms  of  Paradise,  which 
have  a  vigour  and  robustness  of  growth  previously  supposed 
to  belong  only  to  '  crabs.'  " 

Such  is  the  situation  in  regard  to  apple  stocks  and  much 
experimenting  remains  to  be  done  before  a  uniform  type  is 
secured. 

305.  Pear  stocks. — For  the  propagation  of  the  pear  the 
seedlings  are  usually  obtained  from  France  (Mayenne  Prov- 
ince) where  pear  cider  is  made  in  quantity  and  hence  the 
])omace  is  available.  Probably  80  per  cent  of  the  pear  seed- 
lings used  in  this  country  are  imported.  The  seedlings  are 
grown  in  France  as  disease  frequently  ruins  the  crop  when 
the  seed  is  imported  and  an  attempt  made  to  grow  them  here. 

^  Hatton,  R.  G.  Results  of  researches  on  fruit  tree  stocks  at  East 
Mailing.    Jour.  Pomology,  Vol.  2,  No.  1.     1920. 


344  POMOLOGY 

The  pears  collected  for  this  purpose  are  the  native  Pyrus 
communis  of  Europe,  fully  90  per  cent  being  worked  on  this 
stock.  Japanese  sand  pears,  Pyrus  serotina,  are  also  em- 
ployed to  some  extent  and  are  believed  by  some  nurserymen 
to  be  superior  to  the  French  pear  stock.  In  France  this  con- 
tention finds  no  support,  as  nurserymen  there  think  the 
Japanese  stock  is  quite  inferior.  This  stock  is  secured  di- 
rectly from  Japan  or  the  seedlings  are  first  grown  in  France. 
Kieffer  pear  seed  is  also  used  to  a  limited  extent  in  this 
country,  the  seed  being  obtained  from  canning  factories  in 
the  eastern  United  States.  It  will  be  remembered  that  the 
Kieffer  has  as  one  of  its  parents  the  Japanese  sand  pear,  the 
other  being  the  Bartlett. 

306.  Quince  stocks. — The  fruit-bearing  quinces  (Cy~ 
donia  ohlonga)  are  commonly  grown  on  their  own  roots,  i.  e., 
from  cuttings  or  by  mound-layering.  When  worked  on  to 
another  stock,  the  French  Angers  quince  is  most  frequently 
used.  This  Angers  stock  is  grown  from  cuttings,  or  by 
mound-layering  or,  more  rarely,  from  the  seed.  In  rare 
cases,  the  desired  varieties  of  quince  are  root-grafted  on  the 
apple  or  pear  and  the  original  stock  is  cut  away  when  the 
tree  is  moved  to  its  permanent  place  in  the  orchard. 

307.  Peach  stocks. — In  the  eastern  United  States,  peaches 
are  budded  on  stocks  grown  in  this  country.  The  pits  are 
obtained  from  either  seedling  trees  or  standard  varieties, 
but  the  former  are  usually  preferred  as  more  trees  can  be 
grown  to  a  given  measure  of  pits  and  the  trees  are  supposed 
to  be  hardier. 

Pits  produced  the  current  season  give  a  higher  percentage 
of  germination  and  are,  therefore,  selected.  The  plum  (St. 
Julien  and  myrobalan)  is  sometimes  used  for  the  peach,  es- 
pecially in  the  South  and  on  wet  or  heavy  land.  Pits  ob- 
tained in  China  are  being  investigated  in  regard  to  their 
desirability  as  stock  bat  have  not  yet  come  into  use. 


PROPAGATION  AND  FRUIT-STOCKS  345 

308.  Plum  stocks. — In  Europe  and  to  some  extent  in 
this  country,  the  plum  is  propagated  by  suckers  which  arise 
freely  from  the  roots  of  several  of  the  species.  To  make 
use  of  such  suckers,  the  tree  must  of  course  be  on  its  own 
roots.  Mound-layering  and  root-cuttings  are  also  employed 
to  some  extent  with  the  plum  and  in  all  of  the  above  cases 
obtaining  a  stock  is  not  a  problem.  When  plums  are  worked 
on  other  stocks,  the  species  must  be  considered.  P.  domestica 
is  usually  worked  on  seedlings  of  the  same  species,  the  stocks 
being  largely  imported.  The  mj^robalan  (P.  cerasifera)  is 
chiefly  used  for  plums  because  of  its  cheapness  and  because 
it  makes  a  good  union  with  all  varieties;  80  per  cent  of  this 
stock  is  imported.  For  colder  regions,  P.  americana  stocks 
are  preferred.  For  light  soils  the  peach  is  often  taken  as 
a  plum  stock.  Mariamia  (probably  a  hybrid  form  of  myro- 
balan  and  some  native  plum  of  the  Wild  Goose  type),  St. 
Julien,  apricot,  and  almond  are  also  used  as  stock  for  the 
plum.  For  dwarfing,  the  myrobalan  stock  is  employed  as 
is  also  the  mirabelle  (also  a  form  of  P.  cerasifera),  the  P. 
americana,  P.  Munsoniana,  and  P.  angustifolia. 

309.  Cherry  stocks. — Like  the  plum,  the  cherry  will 
grow  readily  from  root-cuttings,  but  it  is  usually  budded  on 
the  seedling  stock.  The  stock  most  commonly  used  is  the 
Mazzard,  a  hardy  and  vigorous  variety  of  the  common  sweet 
cherry  (Prunus  avium).  This  tree  occurs  along  roadsides  in 
the  Central  West  and  the  seed  is  obtained  in  this  country 
to  some  extent,  but  probably  90  per  cent  of  the  cheriy  stock 
is  imported.  The  sour  cherries  are  frequently  worked  on 
the  Mahaleb  (Prunus  Mahaleb)  in  this  country  as  it  makes 
a  congenial  stock  and  the  seedlings  are  relatively  cheap. 
The  Morella  cherries  are  worked  on  the  Mahaleb  stock,  al- 
though Morella  seedlings  are  sometimes  used  to  a  limited 
extent.  P.  pumila  and  P.  Besseyi  are  listed  as  promising 
for  dwarfing  the  cherry. 


346  POMOLOGY 

310.  Quarantine  measures. — For  a  period  of  years  it  had 
become  evident  that  some  measure  should  be  taken  to  stop 
the  introduction  of  foreign  disease  and  insect  pests  which 
were  annually  finding  their  way  to  this  country  on  nursery 
stock  and  other  plants  and  plant  products.  As  a  result,  a 
Plant  Quarantine  Act  was  passed  by  Congress  on  August  20, 
1912,  under  authority  of  which  the  United  States  Depart- 
ment of  Agriculture  has,  from  time  to  time,  issued  various 
quarantine  rulings  which  restricted  or  prohibited  the  im- 
portation of  certain  plants  and  plant  products  found  to 
be  infested  with  noxious  diseases  and  insects.  The  ruling 
which  particularly  affected  the  nursery  and  florist  business, 
and  which  was  strongly  protested  by  special  interests,  was 
known  as  Quarantine  37,  and  was  issued  November  18,  1918. 
This  measure,  together  with  later  interpretations  and  rulings 
thereon,  provides  that: 

"Stocks,  cuttings,  cions,  and  buds  of  fruits  for  propaga- 
tion" and  "seeds  of  fruit,  .  .  .  may  be  imported  from  coun- 
tries which  maintain  inspection,  under  permit  upon  com- 
pliance with  these  regulations,  but,  where  a  particular 
purpose  is  specified,  for  that  purpose  and  no  other.  .  .  .  Im- 
portations of  nursery  stock  and  other  plants  and  seeds  speci- 
fied in  this  regulation,  from  countries  not  maintaining  in- 
spection, may  be  made  under  permit  upon  compliance  with 
these  regulations  in  limited  quantities  for  experimental  pur- 
poses only,  but  this  limitation  shall  not  apply  to  tree  seeds."  ^ 

From  this  ruling  it  will  be  seen  that  fruit-stocks  for  prop- 
agating purposes  are  still  admitted  into  the  United  States, 
but  possibly  the  time  may  come  when  all  such  stocks  must 
be  grown  here. 

311.  Importations  of  stock. — While  no  restriction  was 
placed  on  the  entiy  of  fruit-stocks,  the  impression  went  out 

1  U.  S.  Dept.  Agr.  Off.  of  Sec'y-  Notice  of  Quarantine  37.  Aug.  1, 
1921.    Item  2,  Regulation  3. 


PROPAGATION  AND  FRUIT-STOCKS 


347 


that  there  was  a  faUing  off  of  the  importations.  This  was 
largely  due  to  scarcity  of  stock  in  Europe,  as  a  result  of  war 
conditions,  together  with  a  prohibitive  price  placed  on  this 
stock.  The  following  figures  are  enlightening  on  the  large 
amount  of  stock  imported,  following  the  establishment  of 
quarantine  measures  by  the  United  States  Government: 


Table  XCIII 

importation  of  fruit-stocks,  july  1,  1919,  to  june  30,  1920 
number  of  plants 


Counlru  of 
origin 

Apple 

Plum 

Cherry 

Quince 

Pear 

Persir7i- 
mon 

Un- 
classified 

England 

France 

Holland .... 

Italy 

Japan 

1,825,000 
103,000 

707.S00 

2,808,720 

758,800 
500 

1,107,900 
500 

24,200 

459,900 
300 

Total 

1,928,000 

707,800 

2,S()8,720 

7.59.300 

1,108,400 

24,200 

400,200 

312.  Fruit-trees  on  their  own  roots. — Since  the  fruit- 
tree  above  ground  is  of  the  variety  tlesired,  and  a  part  or  all 
of  the  root  system  is  of  seedling  origin,  it  can  be  seen  that 
considerable  variation  may  be  expected  among  the  trees  of 
any  given  variety.  No  two  of  the  seedlings  used  as  stock 
are  alike  (genetically)  and  they  may  vaiy  markedly  in  vigor 
of  growth,  susceptibility  to  disease  and  insect  pest,  as  well 
as  in  hardiness.  It  is  well  known  to  what  extent  a  dwarfing 
stock  may  influence  the  cion  part,  but  the  smaller  differences 
arc  not  readily  observed  in  the  standard  trees.  In  Australia, 
New  Zealand,  South  Africa,  and  to  some  extent  in  California, 
it  is  recognized  that  Northern  Spy  roots  are  more  resistant 
to  injuiy  by  woolly  aphis  (Schizoneura  lanigera)  than  are  the 
ordinary  crab  roots  and  hence  are  finding  wide  usage.  Some 
varieties  are  more  resistant  to  crown-gall  {Bacterium  tume- 
faciens)  than  are  others,  and  this  is  doubtless  true  also  of 
other  diseases,  pointing  to  an  important  field  of  endeavor 


348  POMOLOGY 

for  the  future.  In  the  prairie  section  of  the  northern  United 
States  and  Canada,  one  of  the  serious  problems  in  fruit- 
growing is  the  damage  done  to  the  roots  of  the  trees  by  low 
temperature,  and  hence  it  is  important  to  secure  stock  which 
is  most  resistant  to  cold. 

The  first  problem  is  the  securing  of  own-rooted  trees. 
Apples  do  not  root  readily  from  stem-cuttings  and  this  proc- 
ess cannot  be  used  commercially  with  the  present  Imowledge 
of  the  subject.  Root-cuttings,  however,  can  be  planted  with 
success,  and  the  method  is  employed  commercially  to  some 
extent. 

The  most  common  process  of  securing  own-rooted  trees 
is  by  the  "long  cion — short  root"  method,  also  known  as  the 
"nurse-root"  method.  Advantage  is  taken  of  the  fact  that 
deeply  planted  root-grafted  trees  will  often  send  out  roots 
from  the  cion,  and  later  (after  two  seasons)  the  trees  are 
dug  and  the  stock  portion  removed.  There  seems  to  be 
great  variation  in  the  ability  of  varieties  to  form  roots. 
Shaw  ^  made  trials  of  over  150  different  varieties  and  species 
to  measure  their  rooting  ability.  There  was  a  variation  of 
rooting  from  0  to  practically  100  per  cent.  A  few  of  those 
exhibiting  a  high  percentage  of  rooting  are:  Arkansas  (77), 
Bailey  Sweet  (95),  Sweet  Bough  (98),  Fameuse  (80),  Opales- 
cent (89),  Primate  (92),  and  Westfield  (83).  Some  exhibiting 
a  low  percentage  of  rooting  may  also  be  cited:  Bethel  (0), 
Black  GiUiflower  (6),  Ensee  (6),  Ingram  (2),  Jeffris  (3), 
Lady  (3),  Ortley  (2),  Paradise  Winter  Sweet  (2),  Red  Canada 
(2),  Tolman  (3),  and  Yellow  Belleflower  (3).  It  cannot  be 
stated  at  present  with  much  definiteness  just  what  factors 
influence  certain  varieties  to  root  freely  from  cions  and 
others  to  root  very  poorly.  The  following  are  suggested  as 
entering  into  the  problem:  a  correlation  between  hardness 
of  wood  and  rooting  ability,  the  softer  the  wood  the  higher 
1  Shaw,  J.  K.    Mass.  Agr.  Exp.  Sta.  Bull.  190.    1919. 


Plate  VIII. — a,  The  twig  terminals  of  these  Baldwin  apple  trees 
were  killed  in  winter  of  1917-18.  b,  A  winter-injured  peach 
tree  that  was  not  cut  back. 


PROPAGATION  AND  FRUIT-STOCKS  349 

the  proportion  rooting  from  the  cion;  fertile,  well-drained, 
sandy  loam,  soils  offer  the  best  conditions  for  securing  a  high 
percentage  of  rooting  trees;  there  seems  to  be  a  relation 
between  the  varietal  ability  to  produce  roots  from  the  cion 
and  the  thickness  of  the  cambium  layer  during  the  dormant 
season. 

313.  Relation  of  cion  and  stock. — Little  has  been  added 
to  the  literature  on  this  subject  during  recent  years  other 
than  that  already  mentioned.  It  has  commonly  been  con- 
sidered that  each  part,  i.  e.,  stock  and  cion,  maintained  its 
own  individuality  with  such  exceptions  as  when  dwarf  trees 
were  produced  by  working  on  slow-growing  stock.  It  was 
argued  that  the  trees  and  fruit  in  an  orchard  of  Baldwin 
apples,  for  example,  were  always  practically  the  same,  allow- 
ing a  reasonable  amount  of  natural  or  continuous  variation, 
and  such  other  differences  as  could  easily  be  traced  to  environ- 
ment factors.  Additional  exceptions  were  noted  occasionally, 
such  as  the  effect  of  a  given  variety  on  the  root  system  as 
could  be  seen  clearly  when  the  trees  were  dug  from  the 
nursery;  and  a  tendency  of  an  individual  tree  to  be  more 
prolific,  earlier  or  later  in  bearing  than  was  usual  for  the 
variety. 

The  question  may  now  be  raised  as  to  whether  the  relation 
of  stock  and  cion  is  not  more  important  than  previously  sup- 
posed, and  whether  the  whole  problem  of  congenial  stocks 
for  fruit  varieties  may  not  need  investigation. 

PROPAGATION    OF   FRUIT-TREES 

In  the  foregoing  paragraphs  it  is  apparent  that  most  of 
the  tree-fruits  are  grown  on  a  foreign  root  system,  i.  e.,  the 
root  parts  are  of  seedling  origin,  largely  for  the  reason  that 
fruit-trees  do  not  "come  true "  from  seed.  It  is  not  the  prov- 
ince of  this  text  to  deal  in  detail  with  the  practice  or  manipu- 
lation of  the  processes  used  in  general  plant  propagation, 


350  POMOLOGY 

but  a  brief  review  of  budding  and  grafting  of  fruit-trees  is 
germane  to  the  general  treatment. 

Layerage. — Layerage  consists  in  taking  advantage  of  the 
habit  of  certain  plants  to  throw  out  roots  from  decumbent 
shoots  and  runners.  Portions  of  the  stems  or  branches  are 
artificially  placed  in  contact  with  the  ground,  either  by  fasten- 
ing them  on  the  surface  or  by  covering  with  soil.  Fruit-trees 
are  not  propagated  in  this  way  with  the  exception  of  a  few 
by  what  is  known  as  "mound-layering."  On  the  other  hand, 
strawberries,  grapes,  raspberries,  gooseberries,  and  many 
ornamentals  are  propagated  by  different  forms  of  layerage. 

314.  Mound-layerage  is  so  termed  because  the  soil 
is  mounded  about  the  base  of  shrubs  or  other  plants  which 
will  throw  out  roots  from  the  stems  when  in  contact  with 
the  soil.  The  several  rooted  portions  are  then  severed  from 
the  mother  plant  and  thus  begin  an  independent  existence. 
The  quince,  gooseberry,  and  several  forms  of  the  Paradise 
apple  arc  propagated  in  this  way. 

315.  Cuttings. — ^None  of  the  commonly  grown  tree- 
fruits  is  propagated  by  means  of  stem-cuttings,  with  the 
exception  of  quinces  which  are  handled  to  some  extent  in 
this  way.  A  number  of  attempts  have  been  made  to  prop- 
agate the  apple  by  cuttings  but  none  has  as  yet  succeeded, 
although  they  may  be  rooted  from  the  cion  by  the  nurse-root 
method  as  previously  described.  The  apple  cuttings  will 
frequently  form  a  callus,  but  such  activity  does  not  favor 
root  development.  Plums  (Marianna)  are  occasionally 
grown  from  cuttings  as  are  also  the  quince  and  persimmon. 
The  grape  and  currant  are  most  commonly  propagated  by 
means  of  cuttings.  Climate  exerts  considerable  influence  on 
the  tendency  of  plants  to  develop  from  cuttings,  the  moist 
warm  southern  sections  being  much  the  more  favorable. 
Root-cuttings  are  commonly  used  in  propagating  such  fruits 
as  have  a  natural  tendency  to  sucker  or  send  up  shoots  from 


PROPAGATION  AND  FRUIT-STOCKS  351 

the  roots.  The  blackberry,  Japanese  quince,  and  to  some 
extent  the  peach,  cherr^'^,  apple,  and  pear  may  be  propagated 
b}^  root-cuttings. 

316.  Grafting  and  budding. — The  arts  of  grafting  and 
budding  are  indispensable  to  the  fruit  industiy,  since  prac- 
tically all  the  tree-fruits  are  propagated  in  this  way.  Both 
processes  involve  the  introduction  of  a  portion  of  one  plant 
into  or  onto  the  living  or  actively  vegetative  portion  of 
another.  In  the  former,  a  piece  of  the  woody  shoot  bearing 
one  or  more  buds  is  used,  while  in  the  latter  one  butl  only  is 
removed  from  the  mother  plant  and  introduced  beneath  the 
bark  and  in  contact  with  the  cambium  of  the  "stock." 
Grafting  is  usually  done  in  early  spring  just  prior  to  or  during 
the  active  period  of  growth,  or  in  the  case  of  root-grafting 
(bench-grafting)  in  the  winter  period.  It  is  usually  desirable 
for  the  cion  material  to  be  in  a  dormant  condition  when  the 
union  is  made,  although  it  is  not  necessarily  fatal  to  have 
the  buds  of  the  cion  l)eginiiing  to  open. 

317.  Tongue-graft  or  whip-graft. — For  the  propagation 
of  nursery  trees  the  tongue-  or  whip-graft  is  most  commonly 
used,  and  the  work  is  performed  in  the  winter.  The  one-  or 
two-year-old  seedling  trees  are  dug  in  the  fall  and  stored 
where  they  can  be  kept  cool,  reasonably  moist,  and  donnant. 
In  Januaiy  or  Februaiy  the  grafting  is  done  in-doors,  which 
gives  it  the  name  bench-grafting.  To  produce  what  the 
nurseiyman  calls  "whole-root"  trees,  the  entire  seedling  root 
is  used,  trimming  off  branching  or  superfluous  parts,  and  the 
cion  is  inserted  into  the  crown  of  the  root.  For  "piece-root " 
grafts  the  seedling  roots  are  divided  into  several  pieces,  about 
3  or  4  inches  long,  thus  securing  several  trees  from  one  root. 
Both  the  cion  and  root  are  severed  with  a  long  oblique  cut 
and  an  incision  is  made  into  the  center  of  these  surfaces  so 
that  the  "tongue"  of  the  cion  will  enter  into  the  incision  of 
the  root,  thus  allowing  the  cambium  areas  to  come  into  con- 


352 


POMOLOGY 


tact.  It  is  not  necessary  but  desirable  that  the  cion  and 
stock  be  of  the  same  diameter.  After  the  two  portions  are 
inserted,  they  are  bomid  tightly  together  with  waxed  string 
or  raffia  and  the  wounded  areas  covered  with  waxed  tape  to 
prevent  the  entrance  of  disease  until  the  wounds  are  calloused. 
These  grafts  are  then  stored  in  sand  or  sawdust  until  early 
spring  when  they  are  planted  in  loose  fer- 
tile soil.  Such  plants  are  allowed  to  remain 
in  the  nurseiy  row  for  one  or  two  years, 
when  they  are  dug  and  are  ready  to  put  on 
the  market. 

The    apple    and    pear    are    often    root- 
grafted,   although   "budded"  trees    of    all 
kinds  are  becoming  more  popular.   (Fig.  38.) 
318.  Budding  is  practiced  entirely  with 
the  "stone  or  drupe"  fruits  in  the  East,  and 
a  large  part  of  the  pome-fruits  are    also 
propagated   in  this  way  at  present.     The 
fact  that  the  budded  tree  has  the  advan- 
tage of  the  entire  root  system  of  the  seed- 
ling, and  that  the  likelihood  of  crown-gall 
is   reduced  by  this  method,   has  made  it 
Fig.  38.  —  The   popular  with  the  trade, 
tongue-  or  whip-       The  essential .  difference  between  grafting 
graft     of    apple.   ^^^  budding,  in  producing  nursery  trees,  is 
craft )  "'^  "  "  merely  that  one  bud  instead  of  several  is 

introduced  into  the  stock.  The  work  is 
usually  done  in  the  latter  part  of  summer  while  the  bark  is 
still  loose  and  will  "work  readily."  A  "bud-stick"  is  cut  from 
the  variety  desired  and  a  shield-shaped  portion  of  the  bark 
is  cut  away  from  the  shoot,  including  a  bud  in  the  center. 
The  leaves  are  removed  as  soon  as  the  " stick"  is  cut,  leaving 
a  small  portion  of  the  petiole  to  be  used  as  a  "handle"  in 
placing  the  bud  into  the  bark  of  the  stock.     A  T-shaped 


PROPAGATION  AND  FRUIT-STOCKS 


353 


incision  is  made  into  the  bark  of  the  seedling  tree  an  inch  or 
two  above  the  ground,  on  the  north  side  of  the  tree  so  that 
the  bud  will  be  shielded  from  the  sun.  The  amateur  usually 
inserts  two  or  three,  one  superimposed  above  the  other,  so 
that  he  may  have  several  chances  of  securing  a  "catch." 
One  only  is  retained  when  growth  starts  in  the  spring. 


Fig.  39. — Shield-budding.     The  bud  tied;  new  growth  of  bud  tied  to 
stock   (the  following  spring);  stub  completely  removed. 


After  inserting  the  bud,  it  is  tied  into  place  with  raffia  or 
cotton  string,  although  the  former  is  preferable.  (Fig.  39.) 
After  the  bud  has  grown  tight,  which  will  be  within  two  weeks 
if  at  all,  the  stricture  is  cut  if  it  has  not  already  loosened. 
The  bud  remains  dormant  until  spring  when  it  begins  growth 
just  as  any  other  bud  on  the  tree.    The  top  of  the  seedling  is 


354 


POMOLOGY 


then  removed,  usually  a  few  inches  above  the  bud  so  that 
the  rapidly  growing  shoot  may  be  loosely  tied  to  the  stub 
to  prevent  breakage.  Later  the  stub  is  removed  to  within 
a  half  inch  above  the  shoot.  If  the  tree  makes  a  growth  of 
three  to  six  feet  the  first  year,  it  is  usually  dug  in  the  fall 
and  stored  for  spring  delivery  to  the  trade,  but  with  the 
apple  and  pear  they  are  frequently  allowed  to  grow  two  years 
in  the  nursery  row  before  being  sold.  The 
peach  should  always  be  dug  at  the  end  of 
the  first  year. 

319.  "  June-budding "  differs  from  the 
usual  method  in  that  "bud-sticks"  are  kept 
over  winter,  usually  on  ice,  until  seedling 
trees  have  made  sufficient  size  by  June  or 
early  July  to  allow  of  budding.  The  bud  of 
the  previous  year  is  inserted  into  this  rapidly 
growing  stock,  which  soon  starts  into  growth 
and  the  top  is  then  removed.  This  gives  a 
"one-year-old"  tree  the  first  season,  thus 
saving  a  year's  time.  This  practice  is  fol- 
lowed in  the  South,  more  especially  with 
the  peach. 

320.  Double-working  of  apple  trees. — To 
Fig.  40 -Method  g^^^j^  certain  of  the  troubles  affecting  the 


of  double-work- 
ing the  apple. 


crowns  and  trunks  of  apple  trees,  such  as 
collar-rot  and  winter-in juiy,  a  method  of 
reworking  nursery  trees  with  varieties  known  to  be 
subject  to  these  troubles  has  come  into  rather  com- 
mon use. 

Trees  of  hardy  or  resistant  varieties  are  secured,  among 
which  may  be  mentioned  Northern  Spy,  Tolman  Sweet,  or 
even  Ben  Davis  for  some  purposes.  Two-  or  three-year-old 
trees  are  preferred,  if  they  are  in  good  condition  and  have 
well-developed  root  systems.    These  are  set  in  the  orchard 


PROPAGATION  AND  FRUIT-STOCKS  355 

in  the  usual  way  and  allowed  to  grow  a  season  in  order  to 
become  well  established. 

Before  the  next  growing  season  begins,  they  are  cut  off 
about  20  to  24  inches  from  the  ground  line  and  grafted  to 
the  desired  variety.  If  the  cions  are  carefully  gathered  and 
labeled,  there  is  the  additional  certainty  of  having  the  va- 
rieties true  to  name;  in  fact  the  double-working  is  sometimes 
done  for  this  purpose. 

A  single  cion  6  to  8  inches  in  length  is  used,  and  in  order 
to  promote  healing  over  of  the  stub  with  the  least  resultant 
weakness  or  deformity,  the  stock  may  be  cut  obliquely  rather 
than  square,  with  the  cion  inserted  in  a  cleft  at  the  top  of 
the  cut,  as  indicated  by  Fig.  40. 

Ordinaiy  grafting-wax  may  be  used  to  cover  the  wound 
but  the  work  is  facilitated  by  the  use  of  waxed  tape,  which 
also  gives  better  support  to  the  cion  until  union  takes  place, 
and  is  more  easily  applied  if  the  work  must  be  done  in  cool 
weather. 

The  nurseiy  trees  may  be  worked  immediately  after  set- 
ting, but  the  chances  of  success  seem  to  be  greater  if  they 
are  first  allowed  to  become  established  in  their  permanent 
location. 


CHAPTER  XV 

STORAGE  OF  FRUIT 

A  great  industry  has  been  developed  since  the  advent  of 
the  cold  storage  plant  and  it  has  become  a  large  factor  in 
handling  the  country's  fruit  crop.  The  details  of  its  com- 
mercial importance  and  economic  value  will  not  be  canvassed 
in  this  text,  but  rather  the  effect  of  storage  on  the  fruit  itself. 

321.  Definition. — Storage  developments  during  the  past 
quarter  of  a  century  represent  a  most  valuable  contribution 
of  science  in  making  perishable  products  available  over  a 
relatively  long  period  of  time.  As  used  in  this  connection, 
storage  usually  refers  to  cool  or  cold  storage  of  products  and 
may  be  defined  as  the  means  by  which  perishable  products  are 
maintained  at  a  temperature  sufficiently  low  to  arrest  disease 
and  the  natural  physiological  and  chemical  processes  of  ul- 
timate maturity  and  decay,  yet  not  sufficiently  low  to  injure 
the  tissue  or  quahty  of  the  materials  stored. 

322.  History^  of  storage.^ — The  idea  of  prolonging  the 
season  of  fruits  and  other  food  products  by  the  means  of 
low  temperatures  is  by  no  means  modem.  Meyer  reports 
cold-storage  methods  applied  to  fruits  in  remote  parts  of 
China,  wholly  out  of  touch  with  civilization.  He  states  that 
the  Chinese  have  practiced  cold  storage  for  centuries."  The 
earliest  efforts  along  this  line  were  to  use  the  natural  caves  or 
artificial  cellars  where  a  fairly  uniform  temperature  from 
50°  to  60°  F.  can  be  maintained  at  all  seasons.     Successful 

1  We  are  indebted  to  "Practical  Cold  Storage"  by  Madison  Cooper, 
Nickerson  and  Collins  Co.,  1914,  for  important  parts  of  this  account. 

-  Stubenrauch,  A.  V.     Storage  and  refrigeration  of  fruits  and  vege- 
tables.   Standard  Cyclo.  Hort.,  Vol.  VI,  p.  3245. 
366 


STORAGE  OF  FRUIT  357 

experimental  refrigeration  by  mechanical  means  was  ac- 
complished as  early  as  the  middle  of  the  eighteenth  century, 
but  no  successful  conmiercial  application  of  cold  storage  was 
evolved  until  after  the  invention  of  Lowe's  carbonic  acid 
machine  in  1867.  The  present  growth  of  the  industiy,  how- 
ever, is  due  to  the  invention  of  the  ammonia  compression 
machine  by  Carl  Linde  in  1875.  The  process  was  first  ex- 
tensively applied  to  the  preservation  of  meats,  fish,  and  the 
like,  but  as  early  as  1881  the  Mechanical  Refrigerating  Com- 
pany of  Boston  opened  a  cold-storage  warehouse,  which 
marks  the  beginning  of  mechanical  refrigeration  as  applied  to 
horticultural  products. 

The  use  of  natural  ice  for  refrigerating  purposes  does  not 
seem  to  have  come  into  general  use  until  comparatively 
modern  times.  The  first  large  ice-house  for  the  storage  of 
natural  ice  was  built  in  1805.  At  first  the  ice  was  packed 
about  the  articles  to  be  preserved,  much  as  is  done  at  present 
in  shipping  fish  and  oysters.  Later  a  chest  or  box  was  used 
in  which  the  ice  was  stored  in  one  end  and  the  products  in 
the  other,  but  such  an  arrangement  lacked  any  means  for 
securing  a  circulation  of  air.  Later  improvements  in  the 
design  of  storage-rooms  called  for  the  storage  of  the  ice  over- 
head with  shafts  allowing  for  a  circulation  of  air,  which 
added  greatly  to  the  success  of  this  type  of  refrigeration. 

323.  Types  of  storage. — As  can  be  inferred  from  the  fore- 
going, there  are  two  general  types  or  systems  of  storage: 
(1)  common,  and  (2)  cold  storage.  The  common,  or  non- 
refrigeration  storage,  refers  to  some  system  by  which  reason- 
ably low  temperatures  can  be  maintained,  either  by  locating 
the  rooms  in  a  cellar,  thus  utilizing  the  low  natural  tempera- 
ture of  the  earth,  or  by  the  use  of  air  currents  to  keep  a  room 
at  the  temperature  of  the  out-door  air. 

The  cold  storage  has  been  evolved  from  the  early  efforts 
at  refrigeration  and  involves  the  cooling  of  the  storage-rooms 


358  POMOLOGY 

by  artificial  agencies,  either  ice  or  mechanical  means  being 
used. 

324.  The  function  of  storage. — It  must  be  recognized 
that  a  fruit  is  a  living  organism  and  life  processes  continue 
until  disintegration  takes  place.  In  common  with  many 
other  organic  products,  the  higher  the  temperature  the 
more  rapid  is  the  disintegration  and,  therefore,  the  func- 
tion of  storage  is  to  delay  the  ripening  process  in  a  tempera- 
ture ^hat  will  not  injure  the  fruit.  It  is  also  designed  to 
retard  the  development  of  diseases  with  which  the  fruit 
may  be  affected,  but  it  cannot  entirely  prevent  their  growth. 

Much  depends  on  the  condition  of  the  fruit  when  it  enters 
storage  as  to  how  long  and  how  well  it  will  keep.  If  the  fruit 
is  over-ripe,  has  been  bruised,  or  is  covered  with  rot  spores, 
the  low  temperature  may  retard  but  cannot  prevent  its 
premature  decay.  ^ 

325.  Factors  influencing  the  keeping  quality  of  fruit. — 
The  following  factors  have  been  outlined  by  Powell  as  af- 
fecting the  keeping  quality  of  fruit  after  it  has  been  placed 
in  cold  storage:  (1)  the  maturity  of  the  fruit  when  picked; 
(2)  the  promptness  with  which  it  is  placed  in  storage;  (3) 
the  temperature  at  which  it  is  stored,  as  well  as  the  uniform- 
ity of  this  temperature;  (4)  influence  of  a  first  wrapper; 
(5)  the  cultural  conditions  under  which  the  fruit  was  pro- 
duced; and  (6)  the  type  of  package  in  which  it  is  stored. 
These  factors  will  be  treated  separately. 

326.  Maturity  of  fruit. — In  considering  the  keeping 
quality  of  fruit,  it  must  of  course  be  recognized  that  this 
is  first  of  all  a  varietal  characteristic  (a  unit  character),  just 
as  much  as  color  and  size.  Also  the  condition  of  the  fruit 
when  it  enters  storage  will  determine  whether  or  not  it  can 
be  kept  for  the  maximum  time  for  the  variety.    Numerous 

1  Powell,  G.  Harold,  and  S.  H.  Fulton.  The  apple  in  cold  storage. 
U.  S.  Dept.  Agr.  Bur.  Plant  Ind.  Bull.  48.    1903. 


STORAGE  OF  FRUIT  359 

tests  have  been  made  to  determine  at  what  stage  of  maturity 
a  fruit  will  keep  best  in  storage.  It  is  well  known  that  an 
under-ripe  apple  will  wilt  and  shrivel  and  an  over-ripe  one 
will  decay  rather  rapidly  even  when  put  in  storage.  It  then 
remains  to  determine  what  is  the  best  time  for  storing  in 
order  to  secure  the  maximum  keeping  quality.  This  stage 
has  been  detennined  as  "hard  ripe,"  i.  e.,  when  the  apple 
has  developed  full  size  and  good  color  for  the  variety.  If  the 
fruit  is  left  on  the  trees  until  the  highest  color  is  developed, 
it  will  often  be  to  the  detriment  of  the  keeping  quality.  The 
proper  time  for  picking  is  usually  associated  with  a  browning 
of  the  seeds,  but  this  is  not  always  a  reliable  guide. 

An  exception  to  this  rule  is  noted  when  apples  are  grown 
on  young  rapidly  growing  trees.  Such  fruit  is  likely  to  be 
overgrown,  and  under  such  conditions  the  apples  will  usually 
keep  better  if  picked  before  fully  grown.  In  general,  as  will 
be  seen  later,  light  colored  apples  scald  worse  in  storage 
than  do  well-colored  ones.  The  following  striking  results  were 
secured  by  the  Department  of  Agriculture  ^  which  demon- 
strate the  value  of  storing  mature  fruit  only.  The  variety 
used  in  this  test  was  the  Rome  Beauty,  which  by  nature  is  a 
long  keeper,  but  subject  to  scald  if  conditions  are  favorable 
for  it.  The  immature  pickings  of  fruit  were  made  during 
the  last  two  weeks  of  September  and  the  mature  pickings 
from  October  2  to  20. 

1  Ramsey,  H.  J.,  A.  W.  INIcKay,  E.  L.  Markell,  and  H.  S.  Bird.    U.  S. 
Dept.  Agr.  Bull.  587.     1917. 


360 


POMOLOGY 


Table  XCIV 
keeping  quality  of  mature  versus  immature  fruit:  rome  beauty  ' 
four-year  average.     (after  ramsey,  markell,  mckay  and  bird) 


Bad 

scald 

Decay 

At  with- 
drawal 

10  daijs 
later 

At  with- 
drawal 

10  days 
later 

First  withdrawal, 

January  8-12 
Mature 

0  0 
0.0 

1.7 
49.9 

0.0 
0.1 

0  1 

Immature 

0  6 

Second  withdrawal, 

February  16-19 
Mature 

0.0 
20.5 

5.4 
70.5 

0.0 
0.0 

0  2 

Immature 

0  0 

Third  withdrawal, 
March  31-April  2 

1.0 

48.9 

10.4 
81.5 

0.0 
0.2 

1  6 

9.8 

Fourth  withdrawal. 

May  4-11 
Mature 

3.5 

58.9 

17.8 
81.6 

0.1 
0.4 

2.7 
18  0 

327.  Effect  of  over-maturity. — As  mentioned  before,  it 
is  very  detrimental  to  the  keeping  quality  of  fruit  to  allow 
it  to  remain  on  the  tree  after  it  is  ready  to  harvest,  i.  e.,  hard 
ripe,  or  to  delay  placing  it  in  storage  immediately  after  it  is 
picked.    8ome  conclusive  experiments  have  been  conducted 

1  Percentage  bad  scald  and  decay  at  withdrawal  from  storage,  and 
after  a  holding  period  of  ten  days  under  market  conditions.  Time 
in  storage  at  first  withdrawal,  3J^  months;  second,  middle  of  February; 
third,  late  March;  and  fourth.  May. 


STORAGE  OF  FRUIT 


361 


by  the  United  States  Department  of  Agriculture  which  point 
to  the  necessity  for  storage  before  the  fruit  is  over-mature 
if  the  best  results  are  to  be  secured.  The  chief  storage 
troubles  from  over-maturity  are  physiological  and  fungous 
decays.  The  following  data  are  taken  from  work  with  the 
Esopus: 

Table  XCV 
effect  of  over-maturity.     esopus. •     ^after  ramsey,  et  al.) 


Decmj 

At  unthdrawal 

10  days  later 

First  withdrawal, 

January  12,  1914 
First  pick 

0.0 
2.3 

1  3 

2  3 

Second  withdrawal, 
February  19,  1914 

0  0 
9.1 

1.3 

Second  pick 

25.0 

Third  withdrawal, 
April  1,  1914 
First  pick 

1.3 
4.0 

2.7 

Second  pick .  . 

2G.0 

Fourth  withdrawal, 

May  4,  1914 
First  pick 

2.7 
14.0 

6.7 

36.0 

At  the  second  withdrawal,  February  19,  which  is  some- 
what later  than  the  usual  commercial  storage  limit  for  this 

1  Percentage  physiological  and  fungous  decay  at  withdrawal  from 
storage,  and  after  a  ten-day  holding  period  under  market  conditions. 
The  first  pick  was  made  September  25,  stored  September  26,  1913. 
The  second  pick  was  October  10  and  stored  October  11,  1913. 


362 


POMOLOGY 


variety,  the  first  picking  was  free  from  decay  oi'  other  storage 
troubles,  while  the  latter  picking  had  developed  9.1  per  cent 
decay.  After  being  held  outside  for  ten  days,  approximating 
the  usual  length  of  time  from  storage  to  consumption,  the 
decay  in  the  late  picking  increased  to  25  per  cent.  The  first 
picking  developed  only  1.3  per  cent  in  the  same  period.  The 
later  inspections  are  well  past  the  commercial  limit  for  the 
variety,  and  the  decay  is  correspondingly  heavier,  though 
still  consistently  less  in  the  first  picking. 

328.  Effect  of  delayed  storage. — As  has  been  seen,  it  is 
important  to  have  fruit  at  the  proper  stage  of  maturity  when 
picked,  but  it  is  also  important  that  it  be  stored  immediately 
or  its  keeping  is  impaired  correspondingly.  In  the  experi- 
ments here  referred  to,  the  fruit  was  picked  at  the  height  of 
the  season  for  the  variety  and  a  portion  stored  in  a  ware- 
house in  a  temperature  but  little  below  that  of  the  outside 
air.  Other  lots  of  the  same  fruit  were  immediately  placed  in 
cold  storage.  In  studying  the  tabulated  results,  it  should 
be  added  that  the  fruit  immediately  stored  "was  always 
brighter,  less  yellow,  and  usually  firmer  than  the  delayed." 
It  will  depend  much  on  the  season  as  to  the  extent  of  damage 
which  results  from  delay  in  storage. 

Table  XCVI 


IMMEDIATE  VERSUS  DELAYED  STORAGE 
FOUR-YEAR   AVERAGE.       JONATHAN.       (AFTER  RAMSEY,   ET  AL.) 


Condition 

First  icith- 

drawal, 
Jan.  9-12 

Second  with- 
drawal, 
Feb.  16-29 

Third  with- 
drawal. 
Mar.  27- 
April  2 

Foxirth  icith- 

drawal, 

May  S-14 

Imm. 

Dd. 

Imm. 

Del. 

Imm. 

Del. 

Imm. 

Del. 

Bad  scald 

At  withdrawal 

10  days  later 

0 
1.0 

0 
1.2 

4.0 
7.3 

.3 
1.2 

0.1 

8  4 

6.7 
90  n 

8.5 
14.7 

6.8 
12.2 

21.5 
35.8 

13.1 

17.5 

17.9 
27.0 

7.8 
12.0 

33.8 
46  4 

Decay 

At  withdrawal 

10  days  later 

4.6       10.3 
10   1        12   7 

13.0 
17  0 

STORAGE  OF  FRUIT  363 

329.  The  storage  temperature. — The  difficulty  under 
many  conditions  is  to  secure  a  uniform  temperature  for  the 
storing  of  fruits.  This  is  an  important  phase  of  the  problem, 
since  fluctuating  temperatures  are  harmful.  The  exact 
temperature  which  is  best  will  depend  somewhat  on  the 
fruit,  the  variety,  the  length  of  time  the  fruit  is  to  be  stored, 
and  perhaps  some  other  factors.  In  general,  however,  the 
minimum  temperature  given  for  a  variety  of  fruit  is  to  be 
preferred  to  a  few  degrees  above,  if  the  maximum  keeping 
is  to  be  secured.  Powell's  experiments  indicate  that  a  tem- 
perature of  31°  or  32°  F.  is  best  for  the  apple  since  the  rots, 
molds,  and  other  diseases  were  retarded  to  a  much  greater 
extent  than  at  35°  to  36°  F.  Cooper,  however,  states  that 
a  temperature  of  30°  F.  is  better  than  any  degree  above 
that,  and  29°  F.  is  practicable  and  advisable  for  long-period 
storing  of  the  better  keeping  varieties.  To  store  safely  at 
29°  to  30°  F.  it  is  necessary  that  a  forced  circulation  of  air 
be  employed.  In  cooling  the  fruit  down  to  the  final  canying 
temperature,  the  refrigeration  must  not  be  applied  too  sud- 
denly. 

Table  XCVII 

STORAGE  TEMPERATURE  FOR  FRUITS.       (aFTER  COOPER) 


Apples 

Oranges 

Lemons 

Plums 

Pears 

Peaches 

Grapes 

Berries,  fresh  (few  days  only^ 
Currants  "       "         " 


30°-31°  F. 

32°-35°  F. 

38°-50° 

32° 

32°-33'' 

32° 

36° 

40° 

32° 


330.  Influence  of  a  fruit  wrapper. — If  each  individual 
fruit  is  wrapped  in  paper  before  placing  in  the  package,  its 


364 


POMOLOGY 


life  will  be  extended  beyond  that  of  unwrapped  fruits.  This 
has  been  particularly  tested  with  apples,  since  they  have  a 
long  period  of  storage.  The  wrapper  affects  the  keeping 
qualities  in  several  different  ways:  it  retards  the  ripening 
processes;  it  prevents  the  transfer  of  rot  from  one  apple  to 
another;  it  protects  against  bruising  and  the  discoloration 
that  maj^  result  from  improper  packing  or  rough  handling; 
it  checks  transpiration;  and  in  general  adds  to  its  commer- 
cial value.     (Powell.) 

A  striking  difference  in  the  keeping  quality  of  wrapped  and 
unwrapped  fruit  is  shown  in  the  following  table: 


Table  XCVIII 
amount  of  decayed  fruit,  april  29,  in  bushel  packages 

(after  POWELL  AND  FULTON) 


Variety 


Unwrapped 


Per  cent 


Baker 

Dickenson 

Mcintosh 

Mcintosh  (second  lot) 

Northern  Spy 

Wagener 

Wealthy 


4.3.0 
15.0 
32.0 
52.0 
63.0 
60.0 


Several  different  types  of  wrappers  were  used  in  these 
experiments — tissue,  parchment,  waxed  or  paraffin,  and  un- 
printed  news — but  no  important  difference  was  observed 
except  with  the  parchment,  on  which  mold  developed  freely 
at  36°  F.  but  only  slightly  at  32°  F. 

A  double  wrapper  proved  more  efficient  in  retarding  ripen- 
ing and  transpiration  than  a  single  one. 


STORAGE  OF  FRUIT  365 

Greene  *  found  a  considerable  variation  in  the  value  of 
wrappers  but  states  that  they  will  extend  the  cold  storage 
season  from  two  weeks  to  several  months,  according  to 
variety  of  fruit.  He  concludes,  however,  that  they  "are  out 
of  the  question  excepting  where  apples  are  packed  in  boxes 
or  where  packed  for  special  purposes  in  barrels."  Much 
the  same  results  are  recorded  in  a  later  report  on  this 
experiment.- 

331.  Influence  of  cultural  conditions. — It  is  well  known 
to  those  who  grow,  store,  and  sell  fruit  that  any  given  variety 
will  vary  somewhat  in  its  keeping  quality,  depending  on 
where  it  is  grown  and  on  the  particular  season.  Apple 
buyers  become  very  discriminating  after  they  are  acquainted 
with  fruit  districts.  Fruit  raised  on  young  trees,  on  low 
land,  and  on  very  light  soils  is  likely  to  have  a  poorer  keeping 
quality  than  fruit  grown  under  the  opposite  conditions. 
However,  it  is  difficult  to  determine  the  keeping  quality  of 
the  product  from  any  given  orchard  except  by  trial,  for  no 
definite  rules  can  be  laid  down  which  will  have  wide  ap- 
plication. 

332.  Type  of  package  for  storage. — The  usual  types  of 
package  for  storage  arc  the  standard  apple  barrel  and  the 
standard  bushel  box.  Other  packages  are  coming  into  use, 
such  as  the  paper  carton  package  of  varying  capacity,  the 
basket  and  the  Boston  bushel  box.  The  barrel  is  used  for  the 
great  bulk  of  the  apples  grown  in  the  eastern  United  States 
but  it  is  not  entirely  satisfactory,  for  it  requires  a  longer  time 
for  the  fruit  throughout  this  package  to  cool  than  is  true  with 
a  smaller  one.  It  is  not  convenient  to  handle  and  consider- 
able bruising  occurs  incident  to  proper  packing.    There  is 

>  Greene,  L.  Cold  storage  for  Iowa  grown  apples.  Iowa  Agr.  Exp. 
Sta.  Bull.  144.    1913. 

2  Whitehouse,  W.  E.  Cold  storage  for  Iowa  apples.  Iowa  Agr.  E.\p. 
Sta.  Bull.  192.     1919. 


366  POMOLOGY 

some  difference  of  opinion  in  regard  to  an  open  and  a  closed 
package.  The  recent  investigation  on  scald  of  apples  shows 
that  aeration  of  the  fruit  is  important  in  preventing  the 
trouble,  which  would  argue  for  a  somewhat  open  package. 
On  the  other  hand,  a  slatted  or  otherwise  open  package 
often  results  in  a  shriveling  of  the  fmit  which  is  veiy  serious 
with  some  varieties. 

333.  The  shrinkage  of  fruit  in  storage. — As  indicated 
before,  the  fruit  in  storage  continues  a  life  process  which 
results  in  certain  changes  and  losses  through  respiration. 
By  far  the  greatest  loss  in  weight,  however,  takes  place 
through  loss  of  moisture  which  amounts  to  about  10  per 
cent  of  the  weight  of  fruit  for  a  season.  The  diy-skinned 
and  russet  apples  lose  moisture  much  more  rapidly  than 
the  oily-skinned  ones.  The  Roxbury  Russet,  Spitzenburg, 
and  Jonathan  shrivel  readily  in  storage  unless  the  humidity 
is  kept  to  nearly  85  per  cent. 

334.  Apple-scald. — The  development  of  scald  is  one  of 
the  serious  problems  to  be  dealt  with  in  the  storage  of  apples. 
Scald  has  been  defined  as  a  "superficial  browning"  of  the 
skin  which  does  not  extend  deep  into  the  flesh  but  detracts 
from  the  appearance  of  the  fruit  and  reduces  its  commercial 
value. 

A  number  of  experiments  have  been  conducted  to  deter- 
mine its  cause  and  how  it  might  be  prevented,  and  as  a  result 
the  following  general  conclusions  have  been  drawn: 

1.  The  cause  of  scald  is  apparently  an  abnormal  respiratory 
condition.  The  disease  can  be  readily  produced  artificially 
by  storing  under  conditions  of  restricted  aeration,  and  no 
scald  can  be  produced  on  apples  that  are  well  aerated.  The 
small  amount  of  scald  that  usually  develops  in  cellar  and 
air-cooled  storage-houses  appears  to  be  explained  by  the 
important  role  that  aeration  plays  in  the  development  of 
the  disease. 


STORAGE  OF  FRUIT  367 

2.  Humidity  apparently  has  no  effect  on  the  development 
of  the  disease,  according  to  Brooks,  Cooley,  and  Fisher, '^ 
while  Whitehouse  found  that  the  drier  the  storage-rooms  the 
less  the  scald. 

3.  All  experiments  showed  that  scald  will  dovc^lop  more 
rapidly  as  the  temperature  increases.  Powell  and  Fulton 
found  that  scald  appeared  to  a  much  greater  extent  if  apples 
were  stored  at  36°  F.  than  at  32°  F.,  although  both  lots 
were  stored  immediately  after  picking.  Brooks  and  Cooley 
found  a  consistent  difference  in  favor  of  the  lower  tempera- 
ture in  the  prevention  of  scald.  Scald  developed  rapidly  at 
50°  F.  during  the  third  month  of  storage,  whereas  it  was 
four  months  before  it  appeared  at  41°  F.,  and  five  months 
at  32°. 

4.  Apple-scald  has  been  more  serious  on  green  than  on 
ripe  fruit,  but  it  develops  more  rapidly  on  the  latter.  All 
investigators  have  laid  emphasis  on  this  point  as  the  most 
important  so  far  as  the  fruit  itself  is  concerned.  "  Immature 
fruit  scalds  readily  in  storage.  Whatever  the  variety  of 
apijles  under  consideration,  it  is  in  the  best  condition  for 
cokl  storage  when  it  has  reached  prime  maturity  for  picking, 
is  well  colored,  hard-ripe,  and  neither  immature  nor  over- 
mature." 

5.  Wrapping  apples  in  paper  delays  the  appearance  of 
scald  during  storage. 

335.  Pre-cooling.'- — It  has  been  determined  that  fruit 
will  cany  better  and  keep  longer  if  it  is  cooled  immediately 
after  it  is  picked  from  the  tree  and  before  going  into  cold 
storage  or  refrigerated  cars.  This  is  particularly  true  of 
citrus  fruits  and  such  soft  kinds  as  peaches. 

Experiments  by  the  United  States  Department  of  Agri- 
culture have  shown  that  it  requires  wann  fniit  from  three  to 

1  Jour.  Agr.  Res.  18:  4.     1919. 

2  Practical  Cold  Storage.    Madison  Cooper.    Second  Ed. 


368  POMOLOGY 

four  days  to  reach  a  temperature  of  45°  F.  when  it  is  placed 
in  a  refrigerator  car,  and  that  the  fruit  was  not  uniformily 
cooled,  the  top  of  the  car  being  from  10°  to  25°  higher  in 
temperature  than  the  floor  and  near  the  ice  bunkers.  Such 
fruit  arrives  at  its  destination  in  poor  condition  and  hence 
entails  heavy  losses  to  the  shippers.  The  greater  part  of 
these  losses  can  be  saved  by  pre-cooling,  providing  the  fruit 
is  in  good  condition  and  well  handled. 

336.  Methods  of  pre-cooling. — Two  general  methods  are 
used  to  effect  the  pre-cooling  of  the  fruit:  (1)  the  car  pre- 
cooling,  and  (2)  the  warehouse  pre-cooling.  The  first  con- 
sists in  loading  the  fruit  in  a  car  ready  for  shipment  and 
then  attaching  a  cold  air  duct  or  chute  to  the  trap  doors 
into  which  ice  is  loaded  into  the  bunkers  or  even  to  the  doors 
of  the  car.  A  fan  forces  the  circulation  of  the  air  through 
the  car  and  the  warmer  air  back  into  a  room  where  it  is 
again  cooled  and  continued  through  the  system  of  circula- 
tion. This  method  seems  to  be  favored  by  transportation 
companies  but  it  is  objected  to  by  the  warehouse  men  be- 
cause the  fruit  is  lowered  in  temperature  so  quickly  that 
injury  to  its  quality  results.  The  temperature  has  been 
lowered  from  80°  or  90°  F. — the  outside  temperature — to 
35°  or  40°  F.  in  one  to  three  hours.  Another  objection  is 
that  space  must  be  left  between  packages  and,  therefore, 
by  the  warehouse  method  from  25  to  50  per  cent  more  fruit 
can  be  loaded  in  a  car.  Neither  is  the  car  of  fruit  cooled  so 
uniformily  as  by  the  other  method. 

In  the  warehouse  method,  the  boxes  of  fruit  are  placed  in 
warehouse  rooms  similar  to  those  of  a  cold  storage  plant 
and  the  temperature  is  lowered  to  the  point  desired  for 
shipping  the  fruit.  The  boxes  are  frequently  handled  on 
endless  belts.  This  system  seems  to  be  gaining  in  favor,  al- 
though the  whole  practice  of  pre-cooling  is  relatively  new 
and  is  not  fully  established. 


STORAGE  OF  FRUIT  369 

It  has  been  suggested  that  if  refrigerator  cars  were  so 
built  as  to  be  as  well  insulated  as  a  modern  cold  storage 
room,  it  would  not  be  necessary  to  ice  cars  in  a  ten-day  haul 
in  summer  weather,  if  they  were  pre-cooled. 


nOPERTY  WMART 
Af.  C.  State  College 


INDEX 


Acid  phosphate,  190 
Adaptation  of  fruit  to  soil  types, 
140 

of  plants  to  soil,  135 

of  species,  237 
Agave  americana,  261 
Alderman,  W.  H.,  294,  307 

mentioned,  212 

quoted,  60,  79,  82 
Alfalfa  in  the  orchard,  208 
Alkaline  soils,  137 
Allen,  F.  W.,  quoted,  270 
Alternate-row  cultivation,  144 
American  plums,  33 
Analysis  of  apple  tree,  92 

of  plant  as  a  guide  to  fertiliza- 
tion, 183 

of  soil  as  a  guide  to  fertiliza- 
tion, 184 
Anomophilous  flowers,  291 
Anthony,  R.  D.,  335 
Apple  oil,  7 

scab,  118 

scald,  366 

seed  for  stock,  339 

stocks,  340,  341 
Apples  at  high  elevations,  9 

at  low  elevations,  9 

quality  in,  7 
Application  of  fertilizers,  215 
Arnold,  Charles,  326 
Arsenical  poisoning  of  trees,  259 
Artificial  pollination,  295 
Ash  of  apple  leaves,  3 

of  fruits,  4 
Auchter,   E.   C,  quoted,   66,  79, 

82,  108,  112 
Averting  injury  from  frosts,  239 


Bacillus  amylovorus,  258,  337 
Bactenum  liimefaciens,  347 
Bailey,  L.  H.,  304,  308,  311,  313 

mentioned,  149 
Ball,  E.  D.,  mentioned,  259 
Ballou,  F.  H.,  mentioned,  189 
Bartlett  pear  in   California,   309 

self-sterile,  309 
Batchelor,  L.  D.,  mentioned,  100 
Beach,  S.  A.,  283,  301 

mentioned,  118 

quoted,  112,  270,  324 
Bedford,  Duke  of,  mentioned,  166 

quoted,  74,  99 
Bending  branches  to  induce  fruit- 
fulness,  67 
Berry,  49 

Biennial  bearing,  Tl 
Bigelow,  W.  D.,  et  al,  12 

referred  to,  115 
Biociimatic  law  of  latitude,  longi- 
tude and  altitude,  234 
Bioletti,  F.  T.,  quoted,  123 
Bizzell,  J.  A.,  mentioned,  162 
Black,  C.  A.,  42 
Black-heart,  259 
Blooming  dates,  248 

period,  duration  of,  249 

season,  247 
Bonasa  wnhellus,  26 
Bone-meal,  191 
Boston  bushel  box,  365 
Bouyoucos,  G.  J.,  mentioned,  157, 

270,  271 
Breaking     limbs     prevented    by 

thinning,  110 
Brooks,  Charles,  367 
Brooks,  W.  P.,  mentioned,  194 


371 


372 


INDEX 


Brown,  G.  G.,  mentioned,  207 
Browne,  C.  A.,  Jr.,  12 
Budding,  351,  352 
Bud  injury,  254 

scales  as  a  protection,  268 

selection,  317 

sports,  320 
Buds,  advantage  of  position,   19 

adventitious-,  23 

axillary-,  23 

branch-,  21 

classification  of,  21 

collateral,  24 

defined,  20 

flower-,  21 

fruit-,  21 

gross  structure  of,  20 

latent-,  23 

lateral-,  23 

leaf-,  21 

mixed-,  22 

simple-,  22 

terminal-,  23 

wood-,  21 
Burbank,  Luther,  316,  330 

Camerarius,  J.,  282 
Canada,  fruit-breeding  in,  325 
Canyons,  effect  on  frost  injury,  273 
Carbohydrates,  54 

relation  to  flowering  of  plants,  56 
Careless  planting,  95 
Carpellary  system,  47 
Castanea  dentata,  136 
Central  leader  tree,  77 
Chance  seedlings,  324 
Chandler,  W.  H.,  81 

mentioned    92,    93,    258,    260, 

264,  265 
Changes  in  composition  of  peach 

during  growth  and  ripening, 

14 
Chemical  changes  in  the  growing 

apple,  10 
nature  of  fruit  soils,  134 


Cherry  stocks,  340,  345 

Chesnut,  V.  K.,  quoted,  6 

Chimeras,  333 

Cion,  339 

Citrus,  bud-variation  of,  322 
fruit-trees,  152 

Clay  soU,  126 

Clean  tillage,  143,  148 

Chmate  defined,  218 
effect  on  fruitfulness,  69 
effect  on  development  of  fruit, 

243 
effect  on   the  floral  structure, 

242 
of  United  States,  228 

Chmatic     provinces     of     United 
States,  229 

Clonal-selection,  316 

Close,  C.  P.,  mentioned,  120 

Cluster  base,  44 

Coates,  Leonard,  321 

Coit,  J.  E.,  332 

Colby,  G.  E.,  4,  5,  9 

Cold  storage,  357 

Collar-rot,  258 

Color  of  fruit,  211 

improved  by  thinning,  109 

Colver,  C.  W.,  9 

Common    salt     as     a    fertilizer, 
191 
storage,  357 

Comparative  morphology  of  fruits, 
48 

Composition  of  apple  fruit,  4 
of  apple  leaves,  2 
of  apples  at  high  elevations,  9 
of  apples  at  low  elevation,  9 
of  apples  in  common  storage,  12 
of  fruits  on  irrigated  land,    9 
of  wood  and  leaves  of  apple,  1 
of  wood  and  leaves  of  peach,  1 
of  wood  and  leaves  of  pear,  1 

Continental  chmates,  225 

Cooley,  J.  S.,  367 

Cooper,  Madison,  363 


INDEX 


373 


Correlation  between  wood  struc- 
ture and  hardiness,  269 

of    trunk    and    twig    measure- 
ments, 168 
Cost  of  thinning,  119 
Cover-crops,  149 

in  California,  151 
Crandall,  C.  S.,  quoted,  288 
Criticisms     of     fertilizer     experi- 
ments, 179 
Cross-pollination,  291 

effect  on  fruits,  292 
Crotch  injury,  257 
Cultivation  and  winter  injur}',  274 
Cultural  practices,  61 
Cuttings,  350 
Cydonia  oblonga,  43,  344 

Danthonia  spicata,  194 

Darwin,   Charles,   283,   291,  292, 

299 
De  Candolle,  A.,  mentioned,  247 
Dehorning  apple  trees,  98 
Delayed  open  center  tree,  77 

storage,  effect  of,  362 
Delaying  blossoming,  239 
Depression,  265 
Depth  of  freezing  in  an  orchard, 

160 
Detjen,  L.  R.,  335 
Devitalizing  of  trees  due  to  root- 
pruning,  64 
Dichogamj',  292 
Dickens,  A.,  mentioned,  99 
Differentiation  of  apple-buds,  35 

carpels,  39 

cherry-buds,  41 

flower-buds,  34 

peach-buds,  41 

petals,  38 

plum-buds,  41 

sepals,  37 

stamens,  38 
Diospyros  Kaki,  295 
Disbudding,  26 


Disease  reduced  by  thinning,  110 

-resistance  dominant,  338 

-resistant  fruits,  337 
Distance  to  thin,  118 
Dorsey,  M.  J.,  221  224 

mentioned  238,  286,  320,  304, 
303,  302 
Double-working  of  trees,  354 
Doucin  stock,  342 
Downing,  A.  J.,  quoted  112, 
Dniinago,  138 
Drinkard,  A.  W.,  Jr.,  64,  65,  67 

mentioned,  100 
Drupe,  48 

Dutch  seedlmg  apples,  342 
Dwarfing  fruit-trees,  68 

of  trees,  explanation  of,  94 

the  cherry,  345 
DjTiamite,  its  use  in  orchards,  177 

Eastern  climatic  province,  230 
Edlefsen,  N.  E.,  quoted,  239 
Effect    of    cultural    methods    on 
yield   of  fruit,    173,    174 
of  leaves  on  parts  surrounding, 

60 
of   location   on   quality,    9 
■    of    moisture   on    the   soil,    153 
of   preceeding   crop   on   winter 

injury,  269 
of  pruning  on  early  bearing,  81 
of  pruning  on  size  and  develop- 
ment of  tree,  78 
of   seed-beanng   on   fruit,    294 
of  sod  on  an  orchard,  171 
of  soil  covering  on  temperature, 

157,  160 
of  thinning  on  total  crop,   113 
of  tillage  on  nitrification,  162 
of  tillage  on  tree  growth,  166, 
168,  171 
Elevations  suitable  for  fruit-grow- 
ing, 228 
Emb\TO  abortion,  290 
Emerson,  Albert,  quoted  329 


374 


INDEX 


Emerson,  R.  A.,  mentioned  274 
Entomophilous,  292 
Essential  oils,  6 
Eutectic  point,  264,  265 
Explosives  for  tillage  purposes,  177 
Exposure  for  fruit-trees,  240 

Fall  plowing  of  orchards,  177 
Farley,  A.  J.,  quoted,  178 
Fertility  removed  by  fruit-trees, 

180 
Fertilization,  process  of,  289 
Fertilizer   experiments,    193,   194, 
198,  200,  202,  203,  205,  206, 
207,  208,  209 
Fertilizing  the  peach,  212 
Fire  danger  in  orchards,  147 
Fisher,  D.  F.,  367 
Fletcher,  S.  W.,  quoted,  105,  293, 

306,  308 
Flowering-branch,  43 
Fortuitous  nature  of  fruits,   311 
Freezing  point  of  sap,  93 
French  stock  defined,  341 
Frost-cracks,  259 
Frost    injury,    character   of,    223 

to  fruits,  238 
"Frozen  to  death,"  261 
Frozen  trees,   treatment  of,   278 
Fruiting  of  the  apple,  26 

apricot,  33 

cherry,  31 

grape,  33 

peach,  29 

pear,  29 

plum,  32 

quince,  33 
Fruiting  system  of  tree,  78 
Fruit  juices,  sugar-content  of,  6 

production  exhaustive,  104 

seeds  for  stock,  handling  of,  339 

soils  of  the  Ozark  region,  128 

soils  of  western  New  York,  129 

-spurs,  24;  vitality  of,  88 

-stocks,  339 


Fruit,  wrapper,  influence  of,  363 
Fulton,  S.  H.,  367 

Garcia,  F.,  299 

mentioned,  121,  242 
Gardner,  V.  R.,  80,  85,  87,  299 

quoted,  68 
Geographical  distribution  of  fruits 

243 
Gideon,  Peter,  328 
Gladwin,  F.  E.,  quoted,  281 
Goff,  E.  S.,  34,  42,  301 

quoted,  286 
Goodspeed,  W.  E.,  quoted,  100 
Gore,  H.  C.  referred,  to  115 
Gould,  H.  P.,  quoted,  112,  116 
Graft  hybrids,  333 
Grafting,  351 
Grape  breeding,  333 

hardiness  of,  281 
Grass  mulch,  143,  145 
Green,  W.  J.,  quoted,  104,  105 
Greene,  L.  365 
Grossenbacher,  J.  G.,  mentioned, 

258,  259 
Guides  to  horticultural  practices, 

233 
Gulf  chmatic  province,  231 

Hail,  224 

Hall,  A.  D.,  mentioned,  123 

Halsted,  B.  D.,  quoted,  270 

Hann,  Juhus,  226,  227 

Hansen,  N.  E.,  325,  329,  330,  338 

hybrids,  329 
Hardiness    of    different     tissues, 

262 
Hardwood-ashes,  191,  203 
Hardy  fruits,  279 

securing,  278 
Headden,  W.  P.,  mentioned,  259 
Heading-back  versus  thinning-out, 

84 
Heat  units,  244 
Hedrick,  U.  P.,  68 


INDEX 


375 


Hcdrick,  mentioned  166,  202,  221, 

223,  251,  271 
quoted,  33,  248,  272,  324,  330, 

334,  335 
Heinicke,  A.  J.,  295 
Hendrickson,  A.  H.,  304,  305 
Henry,  A.  J.,  mentioned,  228 
Herrick,  R.  S., mentioned,  119 
Heterosis,  300 
Heterozygous    nature    of    fruits, 

331 
Hilgard,  E.  W.,  quoted   136,  138, 

153 
History  of  thinning,  102 
Hitchings,  Grant,  mentioned,  145 
Hitt,  Thomas,  quoted,  82,  102 
Hoffmann,  G.  F.,  mentioned,  247 
Homogamy,  292 
Honey  bee  as  a  pollinator,  291, 

301,  305 
Hopkins,  A.  D.,  mentioned,   252 
Hottest  six  weeks,  245 
Howard,  W.  L.,  341 

mentioned  263 
Howe,  G.  H.,  65 
How  freezing  kills,  261 

to  thin,  118 
Humus,  126 

Husmann,  George  C,  67 
quoted,  123 

Ideal  form  of  tree,  78 
Immediate  effect  of  nitrogen  fer- 
tilizers, 189,  207 
Importation  of  stock,  346 
Individuality,  317 

of  trees,  69 
Inflorescence,  42 
Inheritance  in  the  apple,  330 
Insects  and  pollination,  291 

injury  reduced  by  thinning,  110 
Inter-cropping,  143 
Inter-fertility  of  plums,  305 
Inter-sterility  of  almond,  301 

of  cherry,  300 


Inversions  of  temperature,  227 
Iron  salts,  211 
Isochrone  defined,  235 
Isophane  defined,  235 

Japanese  plums,  32 
Jones,  C.  H.,  60 
Jones,  J.  S.,  9 
Jordan,  W.  H.,  quoted,  184 
Jost,  L.,  quoted  51,  52,  53,  54 
June-budtling,  354 
drop,  117 

Keeping     quality,     influence     of 
cultural    conditions    on,    365 

of  fruit,  factors  influencing,  358 
Kerkogamy,  292 
Klebs,  G.,  nu'iitioned,  262 
Knight,  L.  1.,  307 
Knight,    Thomas    Andrew,    282, 

311,313,  321 
Kraus,  E.,  57,  62,  299,  307 

mentioned  88 

quoted  38,  39,  40,  41 
Kraybill,  H.  R.,  57,  62,  88 
Kulisch,  8.,  12 

Layerage,  350 

Leaf  area  of  apple  trees,  170 

-scars,  24 
Length  of  growing  season,  244 
Lewis  C.  I.,  294,  307 

mentioned  100,  190,  207,  214 
Light,     its    effect    on     fruit-bud 

formation,  70 
Lime  for  stone-fruits,  214 

its  application  to  orchard  lands, 
137 

its  function  in  the  soil,  135 
Limestone  soils,  135 
Line-selection,  316 
Loughbridge,  R.  H.,  quoted,  138 
Lovett,  J.  T.,  321 
Lyon,  T.   L.,  mentioned,  162, 

quoted  165 


376 


INDEX 


Macoun,  W.   T.   mentioned  238, 
255,  263,  269,  322 

quoted  327 
Magness,  J.  R.,  16,  60 

quoted  17,  18 
Malus  communis,  341 

mains,  288 
Manures  for  the  orchard,  192,  194, 

202 
Marine  climates,  225 
Mass-selection,  316 
Maturity  of  fruit,  358 

of  tissues,  263 
Mazzard  cherry,  345 
Mechanical  analysis  of  fruit  sods, 

129 
Merchandizing    apples     removed 

by  thinning,  177 
Michigan  fruit-belt,  241 
Minnesota  crab  stock,  342 
Modified  leader  tree,  77 
Moisture,  54 
Molisch,  H.,  265 
Mound-layerage,  350 
Mountain  climates,  226 
Miiller-Thurgau,  H.,  265 
Myer,  F.  N.,  356 

Necessity  of  fertilizing  orchards, 

184 
Nectarines  as  bud-sports,  321 
Nitrate  of  soda,  188 
Nitrates  in  orchard  soils,  161,  162, 

164 
retarded    under   sod,    164 
Nitrification,  150 
Nitrogen-complexes,  54 
Norton,  J.  B.  S.,  mentioned,  251 
Nut,  49 

Objects  of  thinning,  105 
OecaiUhus,  sp.,  225 
Open-headed  tree,  77 
Optima  temperatures  for  plants, 
219 


Orchard  site,  124 

soils,  132 
Organic  matter  in  apple  leaves,  3 

of  orchard  soils,  139 
Organic   versus   inorganic  fertili- 
zers, 187 
Origm    of    apple    varieties,    324 

of  cherry  varieties,  324 

of  peach  varieties,  325 
Over-maturity,  effect  of,  360 
Own-rooted  trees,  347 

Pacific  climatic  province,  233 
Paddock,  W.,  quoted,  228 
Paradise  stock,  342 
Parthenocarpy  defined,  298 
Patten,  C.  G.,  329 
Peach,  changes  in  composition,  14 

stocks,  340,  344 
Pears,  ripening  process  in,  16 

stocks,  337,  340,  343 

varieties  inter-fertile,  308 
Pedicel,  44 

Pedigreed  nursery  stock,  332 
Peduncle,  44 
Periodic  idea,  52 
Pfundt,  M.,  288 
Phenology  defined,  218 
Phosphorous,  190,  198,  208 
Ph3'lloxera-free  grapes,  338 
Physiological  constant,  246 
Pickering,  Spencer,  U.  99 

mentioned,  166 

quoted,  74,  202 
Piece-root  trees,  351 
Pistils  injured  by  cold,  289 
Plains  climatic  province,  232 
Plant  introduction,  323 

Quarantine  Act,  346 
Plants  threatened  by  death,  69 
Plateau  climatic  province,  232 
Plum  stocks,  340,  345 
Pollen  development,  284 

germination,  285 

longevity,  287 


INDEX 


377 


Pollen,  tube-growth,  286,  290 

viability,  287 
Pollination  investigations,  282 
Pome,  48 

Potash,  191,  199,  208,211 
Poultry  in  the  orchard,  62 
Powell,  G.  H.,  321 

quoted,  122,  123,  358,  363,  364, 
367 
Power,  F.  R.,  quoted,  6 
Precautions   relative   to   mulched 

trees,  147 
Pre-cooling,  367 

methods  of,  368 
Price  W.  A.,  mentioned,  93 
Production  of  nuilch  material,  147 
Protection  of  trees  in  winter,  276 
Proteranflrous,  292 
Proterogynous,  292 
Pruning,  63 

and  winter  injury,  275 

definition,  75 

frozen  trees,  94 

mature  trees,  97 

objects  of,  75 

relation  to  nutrition,  88 

root-,  63 

summer-,  63 

tree  at  planting  time,  95 

young  trees,  96 
Prunus  americaiia,  304,  305,  340, 
345 

anguslifolia,  345 

avium,  340,  345 

Besscyi,  329,  345 

cerasifera,  340,  345 

Cerasus,  301 

domestica,  32,  340,  345 

horlulana,  42 

Mahaleb,  340,  345 

Munsoniana,  329,  345 

pennsylvanica,  340 

pumiln,  345 

salicina,  32,  304,  329 

serotina,  43 


Prunus,  virginiana,  44 
Purpose  of  tillage,  173 
Pyramidal  formed  tree,  77,  78 
Pijrus  baccata,  327,  328 

hdulcpfolia,  338 

Calleryana,  338 

communis,  42,  338,  344 

Malus,  42,  288,  327,  328,  341 

ovoidea,  337 

Pashia,  (variolosa)  337 

prunifolia,  327 

serotina,  344 

sinensis,  337,  338 

Quality  in  apples,  7 

of  fruit  improved  by  thinning, 
109 
Quarantine    against    stocks,    346 
Quince  stocks,  340,  344 

Rainfall  221,  231,  233 
Ralston,  G.  S.,  mentioned,  176 
Rapid  fall  of  temperature,  268 
Rate  of  freezing,  267 
Receptive    condition    of    stigma, 

289 
Regular  bearing,  1 1 1 

effect  of  fertilizers  on,  215 
Reimer,  F.  C,  337 

quoted,  189 
Relation   between   blooming   and 
ripening,  251 

of  air  to  soil  temperature,  138 

of  cion  and  stock,  349 

of  leaf  area  to  flowering,  59 

of  stock  and  cion,  339 
Relative  fertility  needs  of  fruit- 
trees    and    farm    crops,     183 
Renovation  pruning,  98 
Reserve  food,  53 

Response  of  young  trees  to  prun- 
ing, 86 
Rest  period,  240,  262 
Ringing,  64 

explanation  of  effects  of,  65 


378 


INDEX 


Ripening  period  of  fruits,  251 

process  in  pears,  16 
Roberts,  R.  H.,  72 
Rogers,  E.  S.,  336 
Rogers'  hybrids,  336 
Root-killing,  260 
Russell,  E.  J.  mentioned,  132 
Russian  fruits,  323,  326 

Sachs,  Julius  Von,  52,  53 
Sand  for  orchard  soils,  126 
Sandsten,  E.  P.,  quoted,  286,  288 
Sap  concentration,  265 
Saunders,  William,  326,  327 
Scale  axis,  43 
Schizoneura  lanigera,  347 
Selection,  methods  of,  314 
Self-fertility,  defined,  297 
Self-pollination,  292 
Self-steriHty,  defined,  297 

in  grapes,  inheritance  of,  334 

of  almond,  301 

of  apple,  307 

of  grape,  301 

of  peach,  306 

of  pear,  308 

of  plum,  304 

of  quince,  307 
Sex  in  the  grape,  inheritance  of, 

334 
Sexual  relation  of  plants,  282,  292 
Shamel,  A.  D.,  320,  322 
Shape  or  form  of  the  tree,  76 
Sharp,  Francis  Peabody,  326 
Shaw,  J.  K.,  7,  348 

quoted,  8,  243 
Shutt,  F.  T.,  3 
Size  of  fruit,  215 

for  thinning,  115 

increased  by  thinning,  106 
Sod  culture,  143,  144 

mulch,  145 
Soil  classification,  125 

color,  134 

defined.  125 


Soil,  for  apple,  133 

for  apple  varieties,  140,  141 

for  cherry,  133 

for  peach,  130,  133, 

for  peach  varieties,  141 

for  pear,  131,  133 

for  plum,  133 

for     Rhode     Island     Greening 
apple,  140 

type  and  depth  of  freezing,  270 

type  and  hardiness,  270 
Sorauer,  P.,  53 
Sour  soils,  136 

Sphceropsis  jnalorurn,  97,  257 
Sprengel,  C.  C,  282 
Spring  frosts,  222 
Sterility,  causes  of,  299 

not  constant,  299 

physiological  causes  of,  300 
Stewart,  J.  P.,  322 

mentioned,  181 

quoted,  175,  198 
Stigmatic  surface,  285 
Stocks  for  grapes,  338 
Stony  soils  for  orchards,  133 
Storage,  defined,  356 

function  of,  358 

history  of,  356 

shrinkage  of  fruit  in,  366 

temperature,  363 

type  of  package  for,  365 
Stripping  trees,  67 
Structure  of  apple  leaves,  170 
Subsoil,  127 
Sugar-content  of  ripe  fruit  juices, 

6 
Sugars  in  fruits,  5 
Sulfate  of  ammonia,  188 
Summer  pruning,  99 
Sun-scald,  260,  268 
Sunshine,  224 

Temperature,  219,  230 
mean  summer,  244 
of  bare  and  tilled  soil,  157 


INDEX 


379 


Temperatures  injurious  to  pollen, 
288 

which  injure  setting  of  fruits, 
238 
Tender  fruits,  279 
Thatcher,  R.  W.,  12 
Theory  of  Knight,  314 

of  pruning,  90 

of  thinning,  103 

of  Van  Mons,  312,  316 
Thinning,  definition,  102 

fruit,  68 

the  grape,  123 

the  peach,  120 

the  pear,  122 

the  plum,  121 
Thompson,  F.,  6 
Thompson,  R.  C,  2 

quoted,  182 
Tibicen  septendecim,  225 
Tillage  and  cover-crops,  143,  149 

of  peach  orchards,  176 

systems,  142 
Time  to  apply  fertilizers,  189 

to  prune,  94 
Tongue-graft,  351 
Topography  of  land,  273 
Top-pruning,  89 
Toxic  theory,  165,  171,  172 
Tufts,  W.  P.,  80,  301,  309 
Two-story  tree,  77,  78 
Type  of  tree,  76 

Under-vegetative  trees,  62 
Unequal  cut,  83 
Unfruitfulness,  causes  of,  283 
Unfruitful  trees,  62 

Valleau,  W.  D.,  335 
Valley  climates,  226 
Value  of  fertilizers  in  tilletl  and 

non-tilled  orchards, 
of    nitrogen    for    the    orchard, 

187 
Van  Mons,  Jean  Baptiste,  311 


Van  Slyke,  L.  L.,  mentioned,  182 
Variation  in  hardiness,  279 
Vascular  anatomy,  44 
Vase-shaped  tree,  77 
Vegetative  and  reproductive  pro- 
cesses, 50 

axis,  44 
Vergon,  F.  P.,  mentioned,  145 
Vermont  crab  stock,  342 
Vigor    of    trees    maintained     by 

thinning,  110 
Vincent,  C.  C,  294,  299,  307 

mentioned,  101 
Virginia  crab  stock,  342 
Vitis  Lahrusca,  33,  333 

rotundijolia,  335 

mnifera,  123,  334,  338 

Waite,  M.  S.,  283,  291,  294,  307, 

308 
Walker,  E.,  quoted.  111 
Warden,  John  A.,  mentioned,  95 
Water-sprouts,  59,  98 
Watrous,  C.  L.,  329 
Waugh,  F.  A.,  283,  289,  304,  307 
Weather,     its    relation    to    fruit 

crops,  219 
Webber,  H.  J.,  quoted,  317 
Wellington,  R.,  quoted,  324,  330 
West,     Frank     L.,     quoted,     239 
When  to  thin,  114 
Whip-graft,  351 
Whipple,  O.  B.,  mentioned,  255 

quoted,  228 
Whitehouse,  W.  E.,  367 
Whitewashing  trees,  276 
Whitten,   J.   C,   mentioned,   238, 

239,  262,  263,  276 
quoted,  321 
Whittier,  A.  C,  6 
Whole-root  trees,  351 
Wicks,  W.  H.,  mentioned,  293 
Wickson,  E.  J.,  mentioned,  119 
Wilder,  H.  J.,  mentioned,  140 
Windbreaks.  224 


380 


INDEX 


Winds,  223,  231 

and  freezing,  273 
Winslow,  R.  M.,  mentioned, 

245 
Winter  injury.  111 

and  bodies  of  water,  272 

due  to  heavy  cropping,  269 


Winter  injury  to  woody  parts,  256 
Woburn  Fruit  Farm,  95 
244,       Woodbury,  C.  G.,  mentioned,  162 
quoted,  153,  167 

Yellow  Newtown  apple,  require- 
ments for,  245 


